Added support for variations in ModalContentPanel. String variation is added with appropriate getters and setters.
Renamed trackModalVisit(IWicketModalVisit) to preShow(ModalContentPanel) to reflect the need for a more generic
hook into the lifecycle of a modal dialog. eg., can set the markup variation on a MessageBox to allow customization of
the MessageBox appearance etc.,
Added support for validators' resource bundles
Code refactored to clean it and avoid API breaks.
[datastores] Add implementations of IDataStore based on Memcached and Apache Cassandra
[datastores] Reimport the datastores
[scala] Add src/main/resources as resource explicitly
[datastores] Extract the session resources management to a specialized class

Next step: implement resources constrains per http session (as PageWindowManager does for DiskDataStore)
[datastores] Implement session resources management for Memcached data store
[datastores] Introduce SessionResourcesManagingDataStore that wraps a real IDataStore and manages the session quota for it
[datastores] Fix Memcached datastore to keep track of the added keys to be able to remove them when the session expire (regression from the previous commit)
[datastores] Add Guava based implementation of MemcachedDataStore.

The benefit is the usage of concurrent map with eviction based on the last access time.
[datastores][common] - Use only the page id for equals/hashcode
[datastores][common] SessionData#size should be volatile
[datastores][common] - Actually log the pageId and sessionId
[datastores][memcached] - Add a test that verifies the Set created from Guava'a Cache has the same eviction capabilities
[datastores] Rename Maven modules
[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)