Processors: entities are not removable

[rr-]

1. Say, we have put Psycho Pass 2nd season into db.
2. It gets deleted from MAL.
3. We still put it in recommendations.
4. Fri goes to admin and refreshes it.
5. It doesn't get deleted from our DB, because:
   1. MALgraph thinks there's error (it doesn't distinguish "entry does not exist on MAL" error from any other error)
   2. Thus, it performs rollback
   3. That way, nothing's changed in our db and the entry remains untouched.

Solution - either:

1. implement manual removal button for fri,
2. make processors understand that entry does not exist anymore and it should be expelled from our db.