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-remote/src/test/scala/akka/remote/NetworkFailureSpec.scala

@@ -9,12 +9,13 @@ import org.scalatest.{ BeforeAndAfterAll, BeforeAndAfterEach }
 import akka.remote.netty.NettyRemoteSupport
 import akka.actor.Actor
 import akka.testkit.AkkaSpec
+import akka.testkit.DefaultTimeout
 import akka.dispatch.Future
 
 import java.util.concurrent.{ TimeUnit, CountDownLatch }
 import java.util.concurrent.atomic.AtomicBoolean
 
-trait NetworkFailureSpec { self: AkkaSpec ⇒
+trait NetworkFailureSpec extends DefaultTimeout { self: AkkaSpec ⇒
   import Actor._
   import akka.util.Duration