ISPN-3530 ISPN-1855 Keep per-cache CH to route requests correctly

* fixed HotRodManagerIT tests: cannot pass null as cache name
ISPN-3950 Move KeyValueFilterFactory and ConverterFactory to core

* Moved to core/ to make it easier for users to implement factory
instances and avoid leaking server/hotrod components.
ISPN-3950 WIP...