Fix ImportError in auth_forms.py
Fix tests.SignalsTests after implementation change
Check checksum in util.key_to_seed

Also other minor defensive programming techniques (lower the key
everywhere it is used, redundant ValueError check in
forms.GridCardActivationForm)
Raise grid card user cache time to 24h

Also make the grid card options configurable from settings.
Merge pull request #1 from koirikivi/changes-20131212

A couple of small changes