[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>

docs/dev/engines/online/annas_archive.rst

@@ -0,0 +1,13 @@
+.. _annas_archive engine:
+
+==============
+Anna's Archive
+==============
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.annas_archive
+   :members:

docs/dev/engines/online/archlinux.rst

@@ -0,0 +1,14 @@
+.. _archlinux engine:
+
+==========
+Arch Linux
+==========
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.archlinux
+  :members:
+

docs/dev/engines/online/bing.rst

@@ -0,0 +1,43 @@
+.. _bing engines:
+
+============
+Bing Engines
+============
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+
+.. _bing web engine:
+
+Bing WEB
+========
+
+.. automodule:: searx.engines.bing
+  :members:
+
+.. _bing images engine:
+
+Bing Images
+===========
+
+.. automodule:: searx.engines.bing_images
+  :members:
+
+.. _bing videos engine:
+
+Bing Videos
+===========
+
+.. automodule:: searx.engines.bing_videos
+  :members:
+
+.. _bing news engine:
+
+Bing News
+=========
+
+.. automodule:: searx.engines.bing_news
+  :members:

docs/dev/engines/online/dailymotion.rst

@@ -0,0 +1,13 @@
+.. _dailymotion engine:
+
+===========
+Dailymotion
+===========
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.dailymotion
+  :members:

docs/dev/engines/online/duckduckgo.rst

@@ -0,0 +1,22 @@
+.. _duckduckgo engines:
+
+=================
+DukcDukGo Engines
+=================
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.duckduckgo
+   :members:
+
+.. automodule:: searx.engines.duckduckgo_images
+   :members:
+
+.. automodule:: searx.engines.duckduckgo_definitions
+   :members:
+
+.. automodule:: searx.engines.duckduckgo_weather
+   :members:

docs/dev/engines/online/google.rst

@@ -0,0 +1,76 @@
+.. _google engines:
+
+==============
+Google Engines
+==============
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+
+.. _google API:
+
+Google API
+==========
+
+.. _Query Parameter Definitions:
+   https://developers.google.com/custom-search/docs/xml_results#WebSearch_Query_Parameter_Definitions
+
+SearXNG's implementation of the Google API is mainly done in
+:py:obj:`get_google_info <searx.engines.google.get_google_info>`.
+
+For detailed description of the *REST-full* API see: `Query Parameter
+Definitions`_.  The linked API documentation can sometimes be helpful during
+reverse engineering.  However, we cannot use it in the freely accessible WEB
+services; not all parameters can be applied and some engines are more *special*
+than other (e.g. :ref:`google news engine`).
+
+
+.. _google web engine:
+
+Google WEB
+==========
+
+.. automodule:: searx.engines.google
+  :members:
+
+.. _google autocomplete:
+
+Google Autocomplete
+====================
+
+.. autofunction:: searx.autocomplete.google_complete
+
+.. _google images engine:
+
+Google Images
+=============
+
+.. automodule:: searx.engines.google_images
+  :members:
+
+.. _google videos engine:
+
+Google Videos
+=============
+
+.. automodule:: searx.engines.google_videos
+  :members:
+
+.. _google news engine:
+
+Google News
+===========
+
+.. automodule:: searx.engines.google_news
+  :members:
+
+.. _google scholar engine:
+
+Google Scholar
+==============
+
+.. automodule:: searx.engines.google_scholar
+  :members:

docs/dev/engines/online/peertube.rst

@@ -0,0 +1,27 @@
+.. _peertube engines:
+
+================
+Peertube Engines
+================
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+
+.. _peertube video engine:
+
+Peertube Video
+==============
+
+.. automodule:: searx.engines.peertube
+  :members:
+
+.. _sepiasearch engine:
+
+SepiaSearch
+===========
+
+.. automodule:: searx.engines.sepiasearch
+  :members:

docs/dev/engines/online/recoll.rst

@@ -0,0 +1,13 @@
+.. _engine recoll:
+
+=============
+Recoll Engine
+=============
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.recoll
+   :members:

docs/dev/engines/online/startpage.rst

@@ -0,0 +1,13 @@
+.. _startpage engines:
+
+=================
+Startpage Engines
+=================
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.startpage
+   :members:

docs/dev/engines/online/torznab.rst

@@ -0,0 +1,13 @@
+.. _torznab engine:
+
+==============
+Torznab WebAPI
+==============
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.torznab
+   :members:

docs/dev/engines/online/wikipedia.rst

@@ -0,0 +1,27 @@
+.. _wikimedia engines:
+
+=========
+Wikimedia
+=========
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+
+.. _wikipedia engine:
+
+Wikipedia
+=========
+
+.. automodule:: searx.engines.wikipedia
+  :members:
+
+.. _wikidata engine:
+
+Wikidata
+=========
+
+.. automodule:: searx.engines.wikidata
+  :members:

docs/dev/engines/online/yahoo.rst

@@ -0,0 +1,13 @@
+.. _yahoo engine:
+
+============
+Yahoo Engine
+============
+
+.. contents::
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+.. automodule:: searx.engines.yahoo
+  :members: