Use gdx-joal for gdx-backend-jogl

It works!
Example on how to update the existing libgdx gdx-invaders project to use the JogAmp JOGL 2
gdx-backend-jogl with gdx-joal.

* 1. First edit the Eclipse project .classpath

demos/invaders/gdx-invaders/.classpath
and change
```xml
       <classpathentry combineaccessrules="false" kind="src" path="/gdx-backend-lwjgl"/>
```

to
```xml
       <classpathentry combineaccessrules="false" kind="src" path="/gdx-backend-jogl"/>
```
* 2. Then Find the main method and switch to use of JoglApplication and JoglApplicationConfiguration

demos/invaders/gdx-invaders/src/com/badlogic/gdxinvaders/GdxInvadersDesktop.java
```java
 package com.badlogic.gdxinvaders;
 
-import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
-import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
+import com.badlogic.gdx.backends.jogl.JoglApplication;
+import com.badlogic.gdx.backends.jogl.JoglApplicationConfiguration;
 
 /** Entry point for desktop version of Gdx Invaders. Constructs an LwjglApplication and registers the renderer.
  * @author mzechner */
 public class GdxInvadersDesktop {
        public static void main (String[] argv) {
-               LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();
+               JoglApplicationConfiguration config = new JoglApplicationConfiguration();
                config.title = "Gdx Invaders";
                config.vSyncEnabled = true;
                config.useGL20 = true;
-               new LwjglApplication(new GdxInvaders(), config);
+               new JoglApplication(new GdxInvaders(), config);
        }
 }
```

* 3.  Thats all! Compile, run and Enjoy.