Separate API and common classes from core

API and Common classes should be extracted from core so that they can be used from other modules without too much depdency baggage. The main use case for this is to reduce the dependencies required by the Hot Rod client.

This would mean creating two new modules: infinispan-api and infinispan-commons.
Infinispan-api would contain the interfaces of the relevant APIs
Infinispan-commons would contain utility classes and common API implementations.