global: translation fixes
global: translation fixes

* Adds configuration file for message extraction.

* Extracts messages from source code files.

* Usage: python setup.py extract_messages -k '_(' \
  -F mapping.cfg -w 100 --input-dirs invenio \
  -o invenio/base/translations/invenio.pot --sort-output

Signed-off-by: Eirini Psallida <d8029defc21e6ed23f32bbbd940d30a709d8ff14@cern.ch>
Reviewed-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio-records,tiborsimko/invenio-records,inveniosoftware/invenio-records,inveniosoftware/invenio-records