remove ActorRef.stop()

- replace ActorRef.stop() by ActorRefFactory.stop(child) everywhere
- ActorCell “optimizes” this to remove the child from its childrenRefs
  in order to allow immediate recycling of the name
- the lost soul must have a place, for which the Locker has been
  created, where Davy Jones will happily rebind the soul to his ship
  (i.e. set “parent” to the locker to avoid mem leak) and periodically
  revisit it (.stop(), in case of that being lost in comm failure,
  similar .watch() to re-check liveness)

akka-actor/src/main/scala/akka/actor/Scheduler.scala

@@ -42,6 +42,15 @@ trait Scheduler {
    */
   def schedule(initialDelay: Duration, frequency: Duration)(f: ⇒ Unit): Cancellable
 
+  /**
+   * Schedules a function to be run repeatedly with an initial delay and a frequency.
+   * E.g. if you would like the function to be run after 2 seconds and thereafter every 100ms you would set
+   * delay = Duration(2, TimeUnit.SECONDS) and frequency = Duration(100, TimeUnit.MILLISECONDS)
+   *
+   * Java API
+   */
+  def schedule(initialDelay: Duration, frequency: Duration, runnable: Runnable): Cancellable
+
   /**
    * Schedules a Runnable to be run once with a delay, i.e. a time period that has to pass before the runnable is executed.
    *