rewrite mailbox selection logic, see #3342

- add “mailbox-requirement” key to dispatcher section
- split out mailbox section, add akka.actor.default-mailbox
- rewrite findMarker method and use it for Props.create() and getting
  the required mailbox of an actor
- add ProducesMessageQueue trait for MailboxType so that requirements
  can be checked before trying to create the actor for real
- verify actor as well as dispatcher requirements for message queue
  before creation, even in remote-deployed case
- change MessageDispatcher constructor to take a Configurator, add that
  to migration guide

akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala

@@ -272,6 +272,14 @@ private[akka] class RemoteActorRefProvider(
           } else if (props.deploy.scope == LocalScope) {
             throw new IllegalArgumentException(s"configuration requested remote deployment for local-only Props at [$path]")
           } else try {
+            try {
+              // for consistency we check configuration of dispatcher and mailbox locally
+              val dispatcher = system.dispatchers.lookup(props.dispatcher)
+              system.mailboxes.getMailboxType(props, dispatcher.configurator.config)
+            } catch {
+              case NonFatal(e) ⇒ throw new IllegalArgumentException(
+                s"configuration problem while creating [$path] with dispatcher [${props.dispatcher}] and mailbox [${props.mailbox}]", e)
+            }
             val localAddress = transport.localAddressForRemote(addr)
             val rpath = (RootActorPath(addr) / "remote" / localAddress.protocol / localAddress.hostPort / path.elements).
               withUid(path.uid)