adjusted the in/de-crement button

adjusted the delta of the slider so the button hav smaller steps in between

Projekte/battleship/client/src/main/java/pp/battleship/client/Menu.java

@@ -59,6 +59,7 @@ public Menu(BattleshipApp app) {
 
         Slider volumeSlider = new Slider();
         volumeSlider.setModel(new DefaultRangedValueModel(0.0 , 2.0, app.getBackgroundMusic().getVolume()));
+        volumeSlider.setDelta(0.1);
         addChild(volumeSlider);
 
         volumeRef = volumeSlider.getModel().createReference();