Prevent wrong language pack imports (containing translations for incorrect locale)

We need to prevent Portuguese issue (French translations in pt_PT).

> * Add some smart automatic language checking during import (e.g. check
> all words in translated message and do not save translation if more
> than 50% of words cannot be translated). That would require
> integration with some translation tool and significantly slow down the
> import process (unless implemented as a separate job)

Maybe we can automate the report and e-mail the results to us. Hopefully if we catch the mistakes early they are not too hard to correct.

Especially if we can automate reversing imports given a set of bad translation ids.