deprecate closure-taking Props factories, see #3081

- base Props on Deploy, Class and Seq[Any] (i.e. constructor args)
- remove deprecated Props usage from akka-docs sample code
- rewrite UntypedActorDocTestBase
- rewrite Java/Scala doc section on actor creation
- add migration guide entry

akka-docs/rst/scala/code/docs/pattern/SchedulerPatternSpec.scala

@@ -88,12 +88,12 @@ class SchedulerPatternSpec extends AkkaSpec {
   }
 
   "send periodic ticks from the constructor" taggedAs TimingTest in {
-    testSchedule(system.actorOf(Props(new ScheduleInConstructor(testActor))),
+    testSchedule(system.actorOf(Props(classOf[ScheduleInConstructor], testActor)),
       3000 millis, 2000 millis)
   }
 
   "send ticks from the preStart and receive" taggedAs TimingTest in {
-    testSchedule(system.actorOf(Props(new ScheduleInConstructor(testActor))),
+    testSchedule(system.actorOf(Props(classOf[ScheduleInConstructor], testActor)),
       3000 millis, 2500 millis)
   }
 }