ISPN-4867 Single event marshaller support more clearly defined in API

* Based on Dan's feedback, Hot Rod server API made it look as if you
could pass a per-factory marshaller but that's not really the case.
A single event marshaller is currently supported.
ISPN-4870 Upgrade to JGroups 3.6.0.Final
ISPN-4913 Add a SKIP_INDEXING flag to HotRod for symmetry with embedded
ISPN-4914 Don't print spurious warning about the isolation attribute on
server startup
ISPN-4911 Add DMR operation for invoking the Mass Indexer
ISPN-4916 Add MassIndexer, XSite State Transfer and Partitioning
ops/attributes to the server RHQ plugin
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