Fixing hardcoded version number in NotificationHandlerTest.
Renaming Update to Ack.

- This also means changing the DataStore interfaces methods that handle
  updates to be consistent.
Refactoring DataStore API.

This is the first of an expected number of commit related to changing
the DataStore API to work well with all kinds of databases (relational
and none-relational).
Moving protocol impl to protocol module.
Removed removeChannel from DataStore interface.
Refactored DefaultSimplePushServerTest to accomodate for usage of different datastore implementations.
Moving DefaultChannel to server-api
Adding JpaSimplePushServerTest
Removing unused imports.
Adding javadoc to MutableChannel
Adding default tokenKey and removing sysout.
Merge branch 'danbev-AGPUSH-381-datastore'
Adding RedisDataStore.
Adding RedisSimplePushServerTest.
Refactoring to be more readable.
Merge branch 'AGPUSH-391-redis'
Adding CouchDB datastore.
Adding CouchDBSimplePushServerTest.
Reducing logging from hibernate.
Adding javadocs and installation links for couchdb.