integrate scrollbar and checkbox art. fixes #215.

OpenRA.Game/Widgets/WorldInteractionControllerWidget.cs

@@ -6,15 +6,14 @@
  * as published by the Free Software Foundation. For more information,
  * see LICENSE.
  */
-#endregion
-
-using System;
-using System.Collections.Generic;
-using System.Drawing;
-using System.Linq;
-using OpenRA.Orders;
+#endregion
+
+using System;
+using System.Drawing;
+using System.Linq;
+using OpenRA.FileFormats;
+using OpenRA.Orders;
 using OpenRA.Traits;
-using OpenRA.FileFormats;
 
 namespace OpenRA.Widgets
 {