legacy: BibClassify port to classifier
legacy: BibClassify port to classifier

* INCOMPATIBLE Removes legacy BibClassify module. (addresses #3233)

* INCOMPATIBLE Refactors the entire classifier module to focus only
  on providing an interface to extract keywords from documents and
  strings. E.g. removal of webinterface, old CLI tool, deamon and
  database models.

* NOTE Renames the main API functions to extract keywords to be:
  get_keywords_from_local_file() and get_keywords_from_text().

Signed-off-by: Jan Aage Lavik <8d55e006a1b29770f275a5c59a7341f17f8e69d5@cern.ch>

tiborsimko/invenio-base,tiborsimko/invenio-base,inveniosoftware/invenio-base,inveniosoftware/invenio-base