Updating the code to use the GCM style publishied at IO 2013.

Previously, the code was based on the older GCM libraries.
Adding a default notifier option
updated compatibility-v4 lib version
avoid more warnings from Android libraries
Add HTTP Basic to Push
Renamed mobileVariantId and mobileSecret
Removing the ability to set a broadcast receiver at runtime.
Updating Android dependency versions
Rename the GCM message receiver
For AGPUSH-229 renaming the 'mobileOperatingSystem' to 'operatingSystem'
Added new prerequisites
Adding in unregister method
Adding REST Provider for Push
Removing setPasswordAuthentication
Extracting Registrar into interface and implementation
Moving AGGCMPushRegistrar to impl package
Refactoring Registrar usage to follow the same pattern as Pipes, Authentication, and DataStores

Registrations was created and is now the factory/manager class for PushRegistrar instances
Moving notificaiton methods to Registrations
Adding a http provider factory so I can inject tests
Removing pushconfig as a parameter for register and unregister