move Building et al into Mods/

OpenRA.Mods.RA/CrateSpawner.cs

@@ -6,13 +6,14 @@
  * as published by the Free Software Foundation. For more information,
  * see LICENSE.
  */
-#endregion
-
-using System;
-using System.Collections.Generic;
-using System.Linq;
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using OpenRA.FileFormats;
+using OpenRA.Mods.RA.Buildings;
 using OpenRA.Traits;
-using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA
 {