ISPN-4528 Genericize remaining M/R internal classes

Master only. See https://issues.jboss.org/browse/ISPN-4528 for more details. 
You know what, I explored this option with genericized MarshalledValue and because MapReduceManager only reads and never creates these values it can not gain much from "genericization". MapReduceManager has to do instanceof on MarshalledValue which erases any typing. I would recommend to genericize MarshalledValue in another PR and commit and start integration of this one.