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 :-)
Most of my testing was focused on JGroups detecting a network splits in a single go. Some real time testing should confirm jgroups behavior, and then ideally to try and bundle view changes into a single one.