Updated 'Node' class.

Updated the 'Node' class by overload the 'isOccupied' method in it.

Projekte/mdga/model/src/main/java/pp/mdga/game/Node.java

@@ -49,4 +49,14 @@ public void clearOccupant() {
     public boolean isOccupied() {
         return occupant != null;
     }
+
+    /**
+     * This method will be used to check if the node is occupied by a piece of the given color.
+     *
+     * @param color as the color of the piece as a Color object.
+     * @return      true or false.
+     */
+    public boolean isOccupied(Color color) {
+        return this.occupant != null && this.occupant.getColor() == color;
+    }
 }