ISPN-2143 Improve how different indexed caches sync up on new indexed types

THIS IS FOR REVIEW ONLY. A proper test for the actual problem it solves is still missing.

* The known classes are no longer kept in a map in QueryInterceptor. They are added in the ClusterRegistry instead (in a unique scope per cache) so the information is automatically disseminated in the cluster. 
* As a consequence, IndexUpdateCommand does not need to propagate the known classes info, this is already taken care of. 
* QueryInterceptor.getKnownclasses method is removed as it's no longer needed
* Also solves ISPN-3597 

Jira: https://issues.jboss.org/browse/ISPN-2143 ,
 https://issues.jboss.org/browse/ISPN-3597

For master only.