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/ActivationTestBase.java

@@ -9,7 +9,6 @@ package docs.camel;
     import akka.util.Timeout;
     import scala.concurrent.Future;
     import scala.concurrent.duration.Duration;
-    import scala.concurrent.duration.FiniteDuration;
     import static java.util.concurrent.TimeUnit.SECONDS;
 //#CamelActivation
 
@@ -17,13 +16,14 @@ import org.junit.Test;
 
 public class ActivationTestBase {
 
+  @SuppressWarnings("unused")
   @Test
   public void testActivation() {
     //#CamelActivation
 
     // ..
     ActorSystem system = ActorSystem.create("some-system");
-    Props props = new Props(MyConsumer.class);
+    Props props = Props.create(MyConsumer.class);
     ActorRef producer = system.actorOf(props,"myproducer");
     Camel camel = CamelExtension.get(system);
     // get a future reference to the activation of the endpoint of the Consumer Actor