[fix] and improve docs generated from source code.

Fix::

    searx/locales.py:docstring of searx.locales.get_engine_locale:17: \
      WARNING: Definition list ends without a blank line; unexpected unindent.

Improvement: don't show default values in the generated documentation whe it is
more a mess than a usefull information (`:meta hide-value:`).

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