ISPN-263 Handle cluster partitions

https://issues.jboss.org/browse/ISPN-263

I added one more commit with some test fixes.
"critical consistency requirements" .. again this is assuming many systems are fine without one, that's misleading as it again hides the fact that state doesn't "heal" on merges.
For example Cassandra users generally don't have critical consistency requirements and are happy with it, but at least it provides a read-repair operation.