BUG 4151 : Create a shared actor system

BUG 4151 : Create a shared actor system

This patch adds an ActorSystemProvider interface in clustering commons
with a method to get a shard ActorSystem instance which uses the
clustered data store configuration as it contains more configuration
options than the rpc connector which pretty much uses stock configuration.
I added a config yang to define an actor-system-provider-service.

I added the ActorSystemProvider implementation and actor-system-provider-impl
config yang in the distributed datastore bundle. I tried it in
sal-clustering-commmons originally but ran into akka errors re: missing
config properties and it also couldn't find the
ReadyLocalTransactionSerializer class. So to avoid chasing down those
errors I put the implementation in sal-distributed-datastore. I think
this makes sense as it is the prime user of the actor system.

I added a dependency for the ActorSystemProvider service in both
datastores modules so the ActorSystem is now injected in and passed
to the DistributedDataStoreFactory. The dependency was also added to the
RPC mpdule.

Elements for the new actor system provider service and impl were added to
the 05-clustering.xml file along with the wiring changes for the data
stores and RPC modules.

Change-Id: I79c14f84c992a2d5ac9c1f1856efbaeba3cc2b77
Signed-off-by: Moiz Raja <moraja@cisco.com>