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
Why don't you return here. No added value to store first in a local variable and then return at the end.