MODE-1746 Minor changes to previous modifications

Several small changes to the previous commit were suggested by Horia,
and implemented with this commit.
MODE-1745 Corrections to Schematic's state transfer

Several issues related to state-transfer were identified and corrected within Schematic's DeltaAware implementation. These primarily dealt with using diff-based deltas when using Infinispan 5.2.0 (tested with Beta6 and later), the implementations of the two deltas (and related classes), and how merges are made, and removal of the NullDelta class.

With these changes, the test projects in MODE-1745 and MODE-1746 work better. There still are problems with state transfer during repository initialization. See MODE-1745 for details.