Bumped compile and target sdk to 21
Renamed GCMReceiver class
Added message receiver class into settings
Set default message receiver for module
Merge branch 'feature/standardisation' into develop

* feature/standardisation:
  Set default message receiver for module
  Added message receiver class into settings
  Renamed GCMReceiver class
  Bumped compile and target sdk to 21
Added register call during settings build
Added annotations to builder
Added setter to setting fields
Merge branch 'feature/auto-register' into develop

* feature/auto-register:
  Added setter to setting fields
  Added annotations to builder
  Added register call during settings build