* Removed need for extra actor that subscribes to cluster
events
* ClusterRouterActor is the router actor and aslo subscribes
* Less scary initialization, and safe calls to createRoutees
* Intercept ClusterDomainEvent to route them to ClusterRouterActor
instead of to the routees
* Ordinary withRouther withDeploy is TOO ugly for this
* Implicit conversion adds withClusterRouter to Props
for Scala API
* Helper method in ClusterRouterPropsDecorator for Java API
* Config max-nr-of-instances-per-node
* selectDeploymentTarget that takes max-nr-of-instances-per-node
and nr-of-instances into account
* Deploy when new member added or removed
* Moved routeeProps to RouteeProvider constructor, needed for
this feature, but also simplifies createRoute, createRoutee,
and resize, since routeeProps doesn't have to be passed around.
* We will write more tests that rely on real Cluster(system) extension,
such as ClusterRoundRobinRoutedActorSpec
* When not using FailureDetectorStrategy or overriding seed nodes
MultiNodeClusterSpec will use the real Cluster(system) extension
instead of a new Cluster instance with additional test facilities
