[docs] reorder chapter "Engines & Settings"

- Split chapter "Engines" and rename it into "Engines & Settings"
- Move docs/admin/engines.rst -> docs/admin/engines/engine_settings.rst

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

docs/dev/reST.rst

@@ -1281,10 +1281,10 @@ Templating
 Templating is suitable for documentation which is created generic at the build
 time.  The sphinx-jinja_ extension evaluates jinja_ templates in the :ref:`make
 install` (with searx modules installed).  We use this e.g. to build chapter:
-:ref:`engines generic`.  Below the jinja directive from the
+:ref:`general engine settings`.  Below the jinja directive from the
 :origin:`docs/admin/engines.rst` is shown:
 
-.. literalinclude:: ../admin/engines.rst
+.. literalinclude:: ../admin/engines/engine_settings.rst
    :language: reST
    :start-after: .. _configured engines:
 

docs/dev/search_api.rst

@@ -20,7 +20,7 @@ Parameters
 
    - :ref:`engines-dev`
    - :ref:`settings.yml`
-   - :ref:`engines generic`
+   - :ref:`general engine settings`
 
 ``q`` : required
   The search query.  This string is passed to external search services.  Thus,