1) When registering with server, indicate that the server should
store messages and send notifications.
2) Process notification GCM messages, and connect to the server
to retrieve actual message content.
1) Break the core cryptography functions out into libaxolotol.
2) The objective for this code is a Java library that isn't
dependent on any Android functions. However, while the
code has been separated from any Android functionality,
it is still an 'android library project' because of the
JNI.
