Concerning akka in osgi:
ActorRefProvider contains in akka-cluster or akka-remote bundle are not found by the akka-actor bundle, thus exposing those if required
    akka-actor and akka-osgi wrapped into one bundle (akka-osgi) taking care of the ActorSystem creation
    The akka modules reference.conf are copied inside this bundle.
    Every other akka module is imported optionnaly,
      the same for com.google.protobuf (already imported in akka-remote)
Merge pull request #985 from Crossing-Tech/osgi-cluster

Concerning akka in osgi: akka-remote/cluster ActorRefProvider exposed to akka-actor
Cluster singleton actor pattern, see #2895

* ClusterSingletonManager
* ClusterSingletonManagerSpec multi-node test
* Use in cluster router with single master sample
* Extensive logging to be able to understand what is
  going on
* Java api
* Add cluster dependency to contrib
* Add contrib dependency to sample
* Scaladoc
* rst docs in contrib area, ref from cluster docs
Merge pull request #1040 from akka/wip-2895-cluster-singleton-patriknw

Cluster singleton actor pattern, see #2895