[mod] replace engines_languages.json by engines_traits.json

Implementations of the *traits* of the engines.

Engine's traits are fetched from the origin engine and stored in a JSON file in
the *data folder*.  Most often traits are languages and region codes and their
mapping from SearXNG's representation to the representation in the origin search
engine.

To load traits from the persistence::

    searx.enginelib.traits.EngineTraitsMap.from_data()

For new traits new properties can be added to the class::

    searx.enginelib.traits.EngineTraits

.. hint::

   Implementation is downward compatible to the deprecated *supported_languages
   method* from the vintage implementation.

   The vintage code is tagged as *deprecated* an can be removed when all engines
   has been ported to the *traits method*.

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

docs/src/searx.enginelib.rst

@@ -0,0 +1,17 @@
+.. _searx.enginelib:
+
+============
+Engine model
+============
+
+.. automodule:: searx.enginelib
+  :members:
+
+.. _searx.enginelib.traits:
+
+=============
+Engine traits
+=============
+
+.. automodule:: searx.enginelib.traits
+  :members:

docs/src/searx.engines.rst

@@ -1,8 +1,8 @@
-.. _load_engines:
+.. _searx.engines:
 
-============
-Load Engines
-============
+=================
+SearXNG's engines
+=================
 
 .. automodule:: searx.engines
   :members:

docs/src/searx.search.processors.rst

@@ -0,0 +1,47 @@
+.. _searx.search.processors:
+
+=================
+Search processors
+=================
+
+.. contents:: Contents
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+
+Abstract processor class
+========================
+
+.. automodule:: searx.search.processors.abstract
+  :members:
+
+Offline processor
+=================
+
+.. automodule:: searx.search.processors.offline
+  :members:
+
+Online processor
+================
+
+.. automodule:: searx.search.processors.online
+  :members:
+
+Online currency processor
+=========================
+
+.. automodule:: searx.search.processors.online_currency
+  :members:
+
+Online Dictionary processor
+===========================
+
+.. automodule:: searx.search.processors.online_dictionary
+  :members:
+
+Online URL search processor
+===========================
+
+.. automodule:: searx.search.processors.online_url_search
+  :members: