Check state of matrices after indexing and rollback if needed

[minimalparts]

This is a tricky one. Once in a while, indexing goes wrong (for whatever reason), and we are not rolling back our matrices properly. At least once this has resulted in an instance stopping to provide search results and I had to recreate the incriminating matrix 'manually'. Not good. We should always check that the database and the most recently changed matrix are in sync. If not, roll back to previous state.

[minimalparts]

I'm linking #56 to this because it seems related.

[minimalparts]

Oh, and we should do the same when deleting resources. The same kind of inconsistency could arise.