make EventHandler non-global

- add Logging trait for nicer interface
- add EventHandlerLogging class for offering the nice interface from
  app.log
- add eventHandler instance to app and use that for all internal logging
  (this means that some places (dispatchers, remoting) were infiltrated
  by app just to do logging, but I think we'll need app in there soon
  enough for other reasons)

akka-testkit/src/test/scala/akka/testkit/TestActorRefSpec.scala

@@ -94,8 +94,6 @@ class TestActorRefSpec extends AkkaSpec with BeforeAndAfterEach {
 
   import TestActorRefSpec._
 
-  EventHandler.start()
-
   override def beforeEach {
     otherthread = null
   }