nearly done, only two known test failures

- moved typed actor factories to app/context (like actor factories)
- fixed a few misplaced supervision changes, all such tests green now
- actually test akka-reference.conf in ConfigSpec
- made DispatcherActorSpec more deterministic (failed intermittently
  here, was due to race towards thread pool)
- wrapped all actor initialization failures into
  ActorInitializationException and made sure that this leads to Stop
- default to Stop on ActorKilledException
- fixed ActorModelSpec to separately supervise the “waves of actors”
  because otherwise the app.guardian is way too busy processing all
  those ChildTerminated messages
- change ActorCell._children from Vector[Stats] to TreeMap[ActorRef,
  Stats] for performance reasons, have not measured memory impact, yet
- ensured that InterrupedException does not leave current thread via
  Failed message to supervisor (wrapped in ActorInterruptedException)
- set core-size=1 and max-size=4 for default dispatcher during test

akka-actor/src/main/scala/akka/routing/Routing.scala

@@ -362,7 +362,7 @@ trait ScatterGatherRouter extends BasicRouter with Serializable {
   private def scatterGather[S, G >: S](message: Any, timeout: Timeout)(implicit sender: Option[ActorRef]): Future[G] = {
     val responses = connectionManager.connections.iterable.flatMap { actor ⇒
       try {
-        if (actor.isShutdown) throw new ActorInitializationException("For compatability - check death first")
+        if (actor.isShutdown) throw ActorInitializationException(actor, "For compatability - check death first", new Exception) // for stack trace
         Some(actor.?(message, timeout)(sender).asInstanceOf[Future[S]])
       } catch {
         case e: Exception ⇒