First pass of refactoring Coordinator Netty pipeline: using common thread pool instead of isolating
Refactoring Coordinator to use standard Netty pipeline which is more scalable than the previous FatClientWrapper design
Restructuring the Voldemort REST server and Coordinator under a common package: voldemort.rest
Changing vector clock serialization to base64 instead of json to improve performance
Revert "Changing vector clock serialization to base64 instead of json to improve performance"

This was part of performance benchmarking. It got wrong pushed to this branch.

This reverts commit fe8479365d8f1eca8f34a09817caa93ed7437dcd.