'git mv' rst resources to md

This is mainly intended to keep the git history as neat as possible.
No actual conversion yet, so now both the rst and the paradox docs
are broken, which will be fixed in the next commits.

akka-docs/src/main/paradox/java/code/jdocs/dispatcher/MyUnboundedMailbox.java

@@ -0,0 +1,51 @@
+/**
+ * Copyright (C) 2009-2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package jdocs.dispatcher;
+
+//#mailbox-implementation-example
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.dispatch.Envelope;
+import akka.dispatch.MailboxType;
+import akka.dispatch.MessageQueue;
+import akka.dispatch.ProducesMessageQueue;
+import com.typesafe.config.Config;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.Queue;
+import scala.Option;
+
+public class MyUnboundedMailbox implements MailboxType,
+  ProducesMessageQueue<MyUnboundedMailbox.MyMessageQueue> {
+
+  // This is the MessageQueue implementation
+  public static class MyMessageQueue implements MessageQueue,
+      MyUnboundedMessageQueueSemantics {
+    private final Queue<Envelope> queue =
+      new ConcurrentLinkedQueue<Envelope>();
+
+    // these must be implemented; queue used as example
+    public void enqueue(ActorRef receiver, Envelope handle) {
+      queue.offer(handle);
+    }
+    public Envelope dequeue() { return queue.poll(); }
+    public int numberOfMessages() { return queue.size(); }
+    public boolean hasMessages() { return !queue.isEmpty(); }
+    public void cleanUp(ActorRef owner, MessageQueue deadLetters) {
+      for (Envelope handle: queue) {
+        deadLetters.enqueue(owner, handle);
+      }
+    }
+  }
+
+  // This constructor signature must exist, it will be called by Akka
+  public MyUnboundedMailbox(ActorSystem.Settings settings, Config config) {
+    // put your initialization code here
+  }
+
+  // The create method is called to create the MessageQueue
+  public MessageQueue create(Option<ActorRef> owner, Option<ActorSystem> system) {
+    return new MyMessageQueue();
+  }
+}
+//#mailbox-implementation-example