[datastores][memcached] Disable the test because it requires a running Memcached server
[datastores][cassandra] Upgrade to latest versions of cassandra-driver-core (1.x and 2.x)

Remove some Maven properties which are inherited
[datastores][cassandra] Fix a typo in a comment
[datastores][redis] Add IDataStore that uses Redis as backend (uses Jedis)
[datastores][common] Fix a bug that the session size was not descresed when a page is removed
[datastores] Make the *DataStoreTest more predictrable by removing the random sleep time
[datastore][redis] Disable the test because it requires a running Redis
Merge branch 'master' into reactive-models