[doc] rearranges Settings & Engines docs for better readability

We have built up detailed documentation of the *settings* and the *engines* over
the past few years.  However, this documentation was still spread over various
chapters and was difficult to navigate in its entirety.

This patch rearranges the Settings & Engines documentation for better
readability.

To review new ordered docs::

   make docs.clean docs.live

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

1 files changed, 0 insertions, 432 deletions

diff --git a/docs/dev/engine_overview.rst b/docs/dev/engine_overview.rst
deleted file mode 100644
index 5fd31c01d..000000000
--- a/docs/dev/engine_overview.rst
+++ /dev/null
@@ -1,432 +0,0 @@
-.. _engines-dev:
-
-===============
-Engine Overview
-===============
-
-.. _metasearch-engine: https://en.wikipedia.org/wiki/Metasearch_engine
-
-.. sidebar:: Further reading ..
-
-   - :ref:`configured engines`
-   - :ref:`settings engine`
-
-.. contents::
-   :depth: 3
-   :backlinks: entry
-
-SearXNG is a metasearch-engine_, so it uses different search engines to provide
-better results.
-
-Because there is no general search API which could be used for every search
-engine, an adapter has to be built between SearXNG and the external search
-engines.  Adapters are stored under the folder :origin:`searx/engines`.
-
-.. _general engine configuration:
-
-General Engine Configuration
-============================
-
-It is required to tell SearXNG the type of results the engine provides. The
-arguments can be set in the engine file or in the settings file (normally
-``settings.yml``). The arguments in the settings file override the ones in the
-engine file.
-
-It does not matter if an option is stored in the engine file or in the settings.
-However, the standard way is the following:
-
-.. _engine file:
-
-Engine File
------------
-
-.. table:: Common options in the engine module
-   :width: 100%
-
-   ======================= =========== ========================================================
-   argument                type        information
-   ======================= =========== ========================================================
-   categories              list        categories, in which the engine is working
-   paging                  boolean     support multiple pages
-   time_range_support      boolean     support search time range
-   engine_type             str         - ``online`` :ref:`[ref] <demo online engine>` by
-                                         default, other possibles values are:
-                                       - ``offline`` :ref:`[ref] <offline engines>`
-                                       - ``online_dictionary``
-                                       - ``online_currency``
-                                       - ``online_url_search``
-   ======================= =========== ========================================================
-
-.. _engine settings:
-
-Engine ``settings.yml``
------------------------
-
-For a more  detailed description, see :ref:`settings engine` in the :ref:`settings.yml`.
-
-.. table:: Common options in the engine setup (``settings.yml``)
-   :width: 100%
-
-   ======================= =========== ==================================================
-   argument                type        information
-   ======================= =========== ==================================================
-   name                    string      name of search-engine
-   engine                  string      name of searxng-engine (file name without ``.py``)
-   enable_http             bool        enable HTTP (by default only HTTPS is enabled).
-   shortcut                string      shortcut of search-engine
-   timeout                 string      specific timeout for search-engine
-   display_error_messages  boolean     display error messages on the web UI
-   proxies                 dict        set proxies for a specific engine
-                                       (e.g. ``proxies : {http: socks5://proxy:port,
-                                       https: socks5://proxy:port}``)
-   ======================= =========== ==================================================
-
-.. _engine overrides:
-
-Overrides
----------
-
-A few of the options have default values in the namespace of engine's python
-modul, but are often overwritten by the settings.  If ``None`` is assigned to an
-option in the engine file, it has to be redefined in the settings, otherwise
-SearXNG will not start with that engine (global names with a leading underline can
-be ``None``).
-
-Here is an very simple example of the global names in the namespace of engine's
-module:
-
-.. code:: python
-
-   # engine dependent config
-   categories = ['general']
-   paging = True
-   _non_overwritten_global = 'foo'
-
-
-.. table:: The naming of overrides is arbitrary / recommended overrides are:
-   :width: 100%
-
-   ======================= =========== ===========================================
-   argument                type        information
-   ======================= =========== ===========================================
-   base_url                string      base-url, can be overwritten to use same
-                                       engine on other URL
-   number_of_results       int         maximum number of results per request
-   language                string      ISO code of language and country like en_US
-   api_key                 string      api-key if required by engine
-   ======================= =========== ===========================================
-
-.. _engine request:
-
-Making a Request
-================
-
-To perform a search an URL have to be specified.  In addition to specifying an
-URL, arguments can be passed to the query.
-
-.. _engine request arguments:
-
-Passed Arguments (request)
---------------------------
-
-These arguments can be used to construct the search query.  Furthermore,
-parameters with default value can be redefined for special purposes.
-
-.. _engine request online:
-
-.. table:: If the ``engine_type`` is :py:obj:`online
-           <searx.search.processors.online.OnlineProcessor.get_params>`
-   :width: 100%
-
-   ====================== ============== ========================================================================
-   argument               type           default-value, information
-   ====================== ============== ========================================================================
-   url                    str            ``''``
-   method                 str            ``'GET'``
-   headers                set            ``{}``
-   data                   set            ``{}``
-   cookies                set            ``{}``
-   verify                 bool           ``True``
-   headers.User-Agent     str            a random User-Agent
-   category               str            current category, like ``'general'``
-   safesearch             int            ``0``, between ``0`` and ``2`` (normal, moderate, strict)
-   time_range             Optional[str]  ``None``, can be ``day``, ``week``, ``month``, ``year``
-   pageno                 int            current pagenumber
-   searxng_locale         str            SearXNG's locale selected by user.  Specific language code like
-                                         ``'en'``, ``'en-US'``, or ``'all'`` if unspecified.
-   ====================== ============== ========================================================================
-
-
-.. _engine request online_dictionary:
-
-.. table:: If the ``engine_type`` is :py:obj:`online_dictionary
-           <searx.search.processors.online_dictionary.OnlineDictionaryProcessor.get_params>`,
-           in addition to the :ref:`online <engine request online>` arguments:
-   :width: 100%
-
-   ====================== ============== ========================================================================
-   argument               type           default-value, information
-   ====================== ============== ========================================================================
-   from_lang              str            specific language code like ``'en_US'``
-   to_lang                str            specific language code like ``'en_US'``
-   query                  str            the text query without the languages
-   ====================== ============== ========================================================================
-
-.. _engine request online_currency:
-
-.. table:: If the ``engine_type`` is :py:obj:`online_currency
-           <searx.search.processors.online_currency.OnlineCurrencyProcessor.get_params>`,
-           in addition to the :ref:`online <engine request online>` arguments:
-   :width: 100%
-
-   ====================== ============== ========================================================================
-   argument               type           default-value, information
-   ====================== ============== ========================================================================
-   amount                 float          the amount to convert
-   from                   str            ISO 4217 code
-   to                     str            ISO 4217 code
-   from_name              str            currency name
-   to_name                str            currency name
-   ====================== ============== ========================================================================
-
-.. _engine request online_url_search:
-
-.. table:: If the ``engine_type`` is :py:obj:`online_url_search
-           <searx.search.processors.online_url_search.OnlineUrlSearchProcessor.get_params>`,
-           in addition to the :ref:`online <engine request online>` arguments:
-   :width: 100%
-
-   ====================== ============== ========================================================================
-   argument               type           default-value, information
-   ====================== ============== ========================================================================
-   search_url             dict           URLs from the search query:
-
-                                         .. code:: python
-
-                                            {
-                                              'http': str,
-                                              'ftp': str,
-                                              'data:image': str
-                                            }
-   ====================== ============== ========================================================================
-
-Specify Request
----------------
-
-The function :py:func:`def request(query, params):
-<searx.engines.demo_online.request>` always returns the ``params`` variable, the
-following parameters can be used to specify a search request:
-
-.. table::
-   :width: 100%
-
-   =================== =========== ==========================================================================
-   argument            type        information
-   =================== =========== ==========================================================================
-   url                 str         requested url
-   method              str         HTTP request method
-   headers             set         HTTP header information
-   data                set         HTTP data information
-   cookies             set         HTTP cookies
-   verify              bool        Performing SSL-Validity check
-   allow_redirects     bool        Follow redirects
-   max_redirects       int         maximum redirects, hard limit
-   soft_max_redirects  int         maximum redirects, soft limit. Record an error but don't stop the engine
-   raise_for_httperror bool        True by default: raise an exception if the HTTP code of response is >= 300
-   =================== =========== ==========================================================================
-
-
-.. _engine results:
-.. _engine media types:
-
-Media Types
-===========
-
-Each result item of an engine can be of different media-types.  Currently the
-following media-types are supported.  To set another media-type as ``default``,
-the parameter ``template`` must be set to the desired type.
-
-.. table::  Parameter of the **default** media type:
-   :width: 100%
-
-   ========================= =====================================================
-   result-parameter          information
-   ========================= =====================================================
-   url                       string, url of the result
-   title                     string, title of the result
-   content                   string, general result-text
-   publishedDate             :py:class:`datetime.datetime`, time of publish
-   ========================= =====================================================
-
-
-.. table::  Parameter of the **images** media type:
-   :width: 100%
-
-   ========================= =====================================================
-   result-parameter          information
-   ------------------------- -----------------------------------------------------
-   template                  is set to ``images.html``
-   ========================= =====================================================
-   url                       string, url to the result site
-   title                     string, title of the result *(partly implemented)*
-   content                   *(partly implemented)*
-   publishedDate             :py:class:`datetime.datetime`,
-                             time of publish *(partly implemented)*
-   img\_src                  string, url to the result image
-   thumbnail\_src            string, url to a small-preview image
-   ========================= =====================================================
-
-
-.. table::  Parameter of the **videos** media type:
-   :width: 100%
-
-   ========================= =====================================================
-   result-parameter          information
-   ------------------------- -----------------------------------------------------
-   template                  is set to ``videos.html``
-   ========================= =====================================================
-   url                       string, url of the result
-   title                     string, title of the result
-   content                   *(not implemented yet)*
-   publishedDate             :py:class:`datetime.datetime`, time of publish
-   thumbnail                 string, url to a small-preview image
-   ========================= =====================================================
-
-.. _magnetlink: https://en.wikipedia.org/wiki/Magnet_URI_scheme
-
-.. table::  Parameter of the **torrent** media type:
-   :width: 100%
-
-   ========================= =====================================================
-   result-parameter          information
-   ------------------------- -----------------------------------------------------
-   template                  is set to ``torrent.html``
-   ========================= =====================================================
-   url                       string, url of the result
-   title                     string, title of the result
-   content                   string, general result-text
-   publishedDate             :py:class:`datetime.datetime`,
-                             time of publish *(not implemented yet)*
-   seed                      int, number of seeder
-   leech                     int, number of leecher
-   filesize                  int, size of file in bytes
-   files                     int, number of files
-   magnetlink                string, magnetlink_ of the result
-   torrentfile               string, torrentfile of the result
-   ========================= =====================================================
-
-.. table::  Parameter of the **map** media type:
-   :width: 100%
-
-   ========================= =====================================================
-   result-parameter          information
-   ------------------------- -----------------------------------------------------
-   template                  is set to ``map.html``
-   ========================= =====================================================
-   url                       string, url of the result
-   title                     string, title of the result
-   content                   string, general result-text
-   publishedDate             :py:class:`datetime.datetime`, time of publish
-   latitude                  latitude of result (in decimal format)
-   longitude                 longitude of result (in decimal format)
-   boundingbox               boundingbox of result (array of 4. values
-                             ``[lat-min, lat-max, lon-min, lon-max]``)
-   geojson                   geojson of result (https://geojson.org/)
-   osm.type                  type of osm-object (if OSM-Result)
-   osm.id                    id of osm-object (if OSM-Result)
-   address.name              name of object
-   address.road              street name of object
-   address.house_number      house number of object
-   address.locality          city, place of object
-   address.postcode          postcode of object
-   address.country           country of object
-   ========================= =====================================================
-
-.. _BibTeX format: https://www.bibtex.com/g/bibtex-format/
-.. _BibTeX field types: https://en.wikipedia.org/wiki/BibTeX#Field_types
-
-.. list-table:: Parameter of the **paper** media type /
-                see `BibTeX field types`_ and `BibTeX format`_
-   :header-rows: 2
-   :width: 100%
-
-   * - result-parameter
-     - Python type
-     - information
-
-   * - template
-     - :py:class:`str`
-     - is set to ``paper.html``
-
-   * - title
-     - :py:class:`str`
-     - title of the result
-
-   * - content
-     - :py:class:`str`
-     - abstract
-
-   * - comments
-     - :py:class:`str`
-     - free text display in italic below the content
-
-   * - tags
-     - :py:class:`List <list>`\ [\ :py:class:`str`\ ]
-     - free tag list
-
-   * - publishedDate
-     - :py:class:`datetime <datetime.datetime>`
-     - last publication date
-
-   * - type
-     - :py:class:`str`
-     - short description of medium type, e.g. *book*, *pdf* or *html* ...
-
-   * - authors
-     - :py:class:`List <list>`\ [\ :py:class:`str`\ ]
-     - list of authors of the work (authors with a "s")
-
-   * - editor
-     - :py:class:`str`
-     - list of editors of a book
-
-   * - publisher
-     - :py:class:`str`
-     - name of the publisher
-
-   * - journal
-     - :py:class:`str`
-     - name of the journal or magazine the article was
-       published in
-
-   * - volume
-     - :py:class:`str`
-     - volume number
-
-   * - pages
-     - :py:class:`str`
-     - page range where the article is
-
-   * - number
-     - :py:class:`str`
-     - number of the report or the issue number for a journal article
-
-   * - doi
-     - :py:class:`str`
-     - DOI number (like ``10.1038/d41586-018-07848-2``)
-
-   * - issn
-     - :py:class:`List <list>`\ [\ :py:class:`str`\ ]
-     - ISSN number like ``1476-4687``
-
-   * - isbn
-     - :py:class:`List <list>`\ [\ :py:class:`str`\ ]
-     - ISBN number like ``9780201896831``
-
-   * - pdf_url
-     - :py:class:`str`
-     - URL to the full article, the PDF version
-
-   * - html_url
-     - :py:class:`str`
-     - URL to full article, HTML version