fix(validation): return errors with predefined keys

eg for unique we return `{'email': {'unique': 1}}`

SD-317
fix(validation): add custom response to rest of used validators

SD-317
fix(users): make password minlength match ui
fix(cache): force cache revalidation
Merge remote-tracking branch 'adrian/master'

Conflicts:
	app.py
fix(tests): add some tolerance to crop file size test