Minor date format update
Fixed typo
ods: gcm registration can be called from main thread in OdsSourceManager

Added GcmRegistrationListener for callbacks about registration.
ods: removed AsyncTask when dealing with gcm registration

AsyncTasks are tied very tightly to activity lifecycles, which is bad
for everyone involved. Current design favours an IntentService and
BroadcastReceiver combination.
Removed GcmTestActivity
ods: added GcmStatus for checking network status
ods: added missing status to GcmIntentService
ods: made GcmUtils public

Needed to be a valid BroadcastReceiver
Added simple test for GcmUtils in MainActivity