ISPN-263 Handle cluster partitions

https://issues.jboss.org/browse/ISPN-263
A good starting point is the documentation commit which describes the implemented functionality.
Most of the code is around playing with state transfer so dan's input is important :-)
I think the comment is still valid.

But it's not clear to me why you want segments not previously owned in the `removedSegments` set. When L1 is enabled, they are also in the the staleL1Segments set.