Remove samples (#22288)

Add code, that was used for documentation to the appropriate projects
or akka-docs.

akka-docs/rst/java/code/docs/cluster/StatsWorker.java

@@ -0,0 +1,30 @@
+package docs.cluster;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import akka.actor.UntypedActor;
+
+//#worker
+public class StatsWorker extends UntypedActor {
+
+  Map<String, Integer> cache = new HashMap<String, Integer>();
+
+  @Override
+  public void onReceive(Object message) {
+    if (message instanceof String) {
+      String word = (String) message;
+      Integer length = cache.get(word);
+      if (length == null) {
+        length = word.length();
+        cache.put(word, length);
+      }
+      getSender().tell(length, getSelf());
+
+    } else {
+      unhandled(message);
+    }
+  }
+
+}
+//#worker