Add some unimplemented proxy classes related to DOMStore

Added basic implementation of DistributedDataStore which does not do much more than fill
in the interface and put tests in place.

All the Proxy classes are still unimplemented.

Change-Id: I9506a05858404a9140f0faf436bd6fb128289693
Signed-off-by: Moiz Raja <moraja@cisco.com>
Merge "Add some unimplemented proxy classes related to DOMStore"