fixup! DB schema update for storing achievements
Remove achievements when flights are deleted
Use mock lib to patch db.session.commit

Otherwise, original function will not be restored if any of assertion
fail.
Separate cleaning and bootstrapping test db.

This will allow generic model tests to pass (they expect totally empty
database)
Recording time when achievement was unlocked
Achievements will be listed in chronological order

When user uploads older flight and existing achievement detected,
that achievement will be linked to that older flight.