Wiki refresh (Hello Update Loop) (#154)

I am going through the beginner wiki pages and updating them so they are the same as the source code files in jme3test/helloworld.

Just a small edit on this file changing the player geometry from protected to private

jme3test/helloworld source code:
https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-examples/src/main/java/jme3test/helloworld/HelloLoop.java

docs/modules/tutorials/pages/beginner/hello_main_event_loop.adoc

@@ -30,7 +30,7 @@ public class HelloLoop extends SimpleApplication {
         app.start();
     }
 
-    protected Geometry player;
+    private Geometry player;
 
     @Override
     public void simpleInitApp() {