[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>

searx/search/processors/online_url_search.py

@@ -20,9 +20,10 @@ class OnlineUrlSearchProcessor(OnlineProcessor):
     engine_type = 'online_url_search'
 
     def get_params(self, search_query, engine_category):
-        """Returns a set of *request params* or ``None`` if search query does not match
-        to at least one of :py:obj:`re_search_urls`.
+        """Returns a set of :ref:`request params <engine request online>` or ``None`` if
+        search query does not match to :py:obj:`re_search_urls`.
         """
+
         params = super().get_params(search_query, engine_category)
         if params is None:
             return None