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/java/code/docs/camel/sample/quartz/QuartzSample.java

@@ -6,7 +6,7 @@ import akka.actor.Props;
 public class QuartzSample {
   public static void main(String[] args) {
     ActorSystem system = ActorSystem.create("my-quartz-system");
-    system.actorOf(new Props(MyQuartzActor.class));
+    system.actorOf(Props.create(MyQuartzActor.class));
   }
 }
 //#QuartzExample