plugins: added google play services lib
Added googleApiKey
ods: added basic ods receiver and utils for registering
ods: minor renaming
ods: minor javadoc update
ods: GcmUtils deals with OdsSources instead of simple strings
ods: minor rename in GcmUtils
ods: moved GcmException to different file
ods: added more helper methods to OdsSourceManager
ods: name cleanup in OdsSourceManager

There are three ways to receive data from the ods now:
- Manual sync (bad)
- Polling (not sooo bad)
- Push notifications (better)
pegelonline: use localhost ods server while commits are pending
monitor: db operations no longer run on main thread
Added basic skeleton for GcmTestActivity
Added basic Gcm un-/registration test