reduce batch count a LOT; build palette order is now explicit

OpenRA.Game/Traits/Buildable.cs

@@ -31,6 +31,7 @@ namespace OpenRA.Traits
 		public readonly string LongDesc = "";
 		public readonly string Icon = null;
 		public readonly string[] AlternateName = { };
+		public readonly int BuildPaletteOrder = 0;
 	}
 
 	class Buildable { }