added functional and unit tests for PATCH.  Added interfaces
TK-116225 Changd the generic type to be more standard
TK-116225 Updated the interface to reflect what a patch should do
TK-116225 Renamed method in patchable interface to cause less confusion when discussing it
TK-116225 Updtaed DistributedDatastore patch method to more closely match that of Datastore
TK-116225 Updated EHcache datatstore for changes to dataqstore contract. (not implemented yet though)
B-58103 Updated the interfaces again to reflect other changes
TK-116206 ADded patch to ehcache datastore