move all Ask stuff to akka.pattern

- remove ?(msg, timeout), should always use ?(msg)(timeout) because of
  Scala’s only Martin-acknowledged design flaw of being able to pass
  tuples into single-arg methods without adding another pair of parens
- put a provider into all actor refs, because they all are created by
  and associated with one
- treat all terminated refs equally: tell(msg) and return broken promise

akka-docs/scala/code/akka/docs/actor/ActorDocSpec.scala

@@ -252,7 +252,7 @@ class ActorDocSpec extends AkkaSpec(Map("akka.loglevel" -> "INFO")) {
     //#using-explicit-timeout
     import akka.util.duration._
     import akka.pattern.ask
-    val future = myActor ? ("hello", timeout = 500 millis)
+    val future = myActor.ask("hello")(500 millis)
     //#using-explicit-timeout
     Await.result(future, 500 millis) must be("hello")
   }