Remove SelfActorRef and use ActorContext to access state in ActorInstance. See #1202

- removed SelfActorRef
- added an ActorContext interface that provides a view into ActorInstance
- the ActorInstance (as ActorContext) gets injected into the Actor
- moved self methods like sender and reply directly to the Actor

akka-tutorials/akka-tutorial-second/src/main/scala/Pi.scala

@@ -38,7 +38,7 @@ object Pi extends App {
 
     def receive = {
       case Work(arg, nrOfElements) ⇒
-        self reply Result(calculatePiFor(arg, nrOfElements)) // perform the work
+        reply(Result(calculatePiFor(arg, nrOfElements))) // perform the work
     }
   }
 
@@ -66,7 +66,7 @@ object Pi extends App {
         for (arg ← 0 until nrOfMessages) router ! Work(arg, nrOfElements)
 
         //Assume the gathering behavior
-        this become gather(self.channel)
+        this become gather(channel)
     }
 
     // phase 2, aggregate the results of the Calculation