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/remoting/RemoteDeploymentDocTestBase.java

@@ -48,7 +48,7 @@ public class RemoteDeploymentDocTestBase {
     addr = AddressFromURIString.parse("akka.tcp://sys@host:1234"); // the same
     //#make-address
     //#deploy
-    ActorRef ref = system.actorOf(new Props(SampleActor.class).withDeploy(
+    ActorRef ref = system.actorOf(Props.create(SampleActor.class).withDeploy(
       new Deploy(new RemoteScope(addr))));
     //#deploy
     assert ref.path().address().equals(addr);
@@ -58,7 +58,7 @@ public class RemoteDeploymentDocTestBase {
   public void demonstrateSampleActor() {
     //#sample-actor
 
-    ActorRef actor = system.actorOf(new Props(SampleActor.class), "sampleActor");
+    ActorRef actor = system.actorOf(Props.create(SampleActor.class), "sampleActor");
     actor.tell("Pretty slick", null);
     //#sample-actor
   }