Introduce parental supervision, BUT TESTS ARE STILL FAILING

- every actor is now supervised, where the root of the tree is
  app.guardian, which has its supervisor field set to a special ActorRef
  obtained from provider.theOneWhoWalksTheBubblesOfSpaceTime (this name
  is meant to indicate that this ref is outside of the universe, cf.
  Michio Kaku)
- changed all tests to obtain specially supervised children (i.e. not
  top-level) via (supervisor ? Props).as[ActorRef].get
- add private[akka] ScalaActorRef.sendSystemMessage for sending
  Supervise()
- everything routing or remote is broken wrt. supervision, as that was
  not “properly” implemented to begin with, will be tackled after
  app/supervision/eventbus/AkkaSpec are stabilized enough

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

@@ -94,7 +94,7 @@ object Routing {
  * An Abstract convenience implementation for building an ActorReference that uses a Router.
  */
 abstract private[akka] class AbstractRoutedActorRef(val props: RoutedProps) extends UnsupportedActorRef {
-  private[akka] val uuid: Uuid = newUuid
+  private[akka] override val uuid: Uuid = newUuid
 
   val router = props.routerFactory()
 
@@ -120,14 +120,14 @@ abstract private[akka] class AbstractRoutedActorRef(val props: RoutedProps) exte
  * A RoutedActorRef is an ActorRef that has a set of connected ActorRef and it uses a Router to send a message to
  * on (or more) of these actors.
  */
-private[akka] class RoutedActorRef(val routedProps: RoutedProps, val address: String) extends AbstractRoutedActorRef(routedProps) {
+private[akka] class RoutedActorRef(val routedProps: RoutedProps, override val address: String) extends AbstractRoutedActorRef(routedProps) {
 
   @volatile
   private var running: Boolean = true
 
-  def isShutdown: Boolean = !running
+  override def isShutdown: Boolean = !running
 
-  def stop() {
+  override def stop() {
     synchronized {
       if (running) {
         running = false