moved the GitDataStore into fabric-core as its way too hard to have plugable DataStores in separate bundles right now.
this change adds git into fabric-core and I've had to move FabricGitService interface to fabric-core from fabric-git (which adds a fabric-core dependency on fabric-git - we could move FabricGitService into a separate bundle later if this proves troublesome). Other than that right now we still hard code the ZooKeeperDataStore with DS as being the only implementation; this change was really about moving things around and checking I'd not broken anything ;). Next we can try have a smarter DataStore factory which picks the DataStore to use based on configuration (and does the same on bootstrap time too)