Cleanup of methods in Actor and ActorContext trait. See #1377

* Added JavaActorContext, UntypedActor.getContext
* implicit val context in Actor needs to be implicit to support forward,
it would be nice if it wasn't implicit because now I can't override context
in UntypedActor
* Removed implicit def system in Actor
* Removed implicit def defaultTimeout in Actor
* Removed receiveTimeout, children, dispatcher, become, unbecome, watch,
unwatch in Actor
* Removed corresponding as above from UntypedActor
* Removed implicit from dispatcher in ActorSystem
* Removed implicit def timeout in TypedActor
* Changed receiveTimeout to use Duration (in api)
* Changed many tests and samples to match new api

akka-docs/general/code/ConfigDocSpec.scala

@@ -15,7 +15,7 @@ class ConfigDocSpec extends WordSpec with MustMatchers {
     //#custom-config
     val customConf = ConfigFactory.parseString("""
       akka.actor.deployment {
-        /app/my-service {
+        /user/my-service {
           router = round-robin
           nr-of-instances = 3
         }