Merger: Add is_movie flag so that movies get a custom URI

Movie URI now is like .../movie/<UUID> instead of .../generic/UUID
Merge remote-tracking branch 'origin/master'

* origin/master:
  TMDb Mapper: Change ID field to TMDb ID
  Change ID field to TMDb ID
  Freebase-Crawler: ensured (more or less) that an API key is specified
  DBpedia-Mapper: small but fix to avoid problems with nil