Open source changes for high density caching impl

- Serialization module improved to support multiple Data storage types
- Introduced Node & Client extensions (to support serialization abstractions)
- Improved partition service to support high density caching 
 
See https://github.com/hazelcast/hazelcast-enterprise/pull/66
Should this exception not be propaged? After it is logged, it is lost... the caller has no way of knowing something went wrong.