Added ugly layer buttons

scopviz/src/main/java/de/tu_darmstadt/informatik/tk/scopviz/main/GUITheme.css

@@ -1,17 +1,17 @@
 .underlayButton{
-	-fx-background-image: url('/de/tu_darmstadt/informatik/tk/scopviz/main/default_button.png');
+	-fx-background-image: url('/de/tu_darmstadt/informatik/tk/scopviz/main/underlay_button.png');
   -fx-background-repeat: no-repeat;
   -fx-background-position: center
 }
 
 .operatorButton{
-	-fx-background-image: url('/de/tu_darmstadt/informatik/tk/scopviz/main/default_button.png');
+	-fx-background-image: url('/de/tu_darmstadt/informatik/tk/scopviz/main/operator_button.png');
   -fx-background-repeat: no-repeat;
   -fx-background-position: center
 }
 
 .mappingButton{
-	-fx-background-image: url('/de/tu_darmstadt/informatik/tk/scopviz/main/default_button.png');
+	-fx-background-image: url('/de/tu_darmstadt/informatik/tk/scopviz/main/mapping_button.png');
   -fx-background-repeat: no-repeat;
   -fx-background-position: center
 }