add a hook for reacting on user deletion.
fix issues with storing and retrieving the sequence

.to_i makes retrieving the sequence more robust - in particular if the file content was not meaningful.
store_seq should also be called if it was a destroy action.
delete user db's on user deletion.
use our logger - not just puts
Merge pull request #2 from azul/feature/delete-user-databases

Delete per user databases if the user has been deleted