[fix] searx_extra/update scripts: set_loggers(wikidata, 'wikidata') (#331)

* [fix] searx_extra/update scripts: set_loggers(wikidata, 'wikidata')

To test use::

    ./manage pyenv.cmd searx_extra/update/update_currencies.py
    ./manage pyenv.cmd searx_extra/update/update_osm_keys_tags.py
    ./manage pyenv.cmd searx_extra/update/update_wikidata_units.py

The script `update_engine_descriptions.py` seems to have some issues not related
to this patch.

    ./manage pyenv.cmd python -m pip install -U pycld3
    ./manage pyenv.cmd searx_extra/update/update_engine_descriptions.py

Closes: https://github.com/searxng/searxng/issues/328


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