move CYard trait and UndeployMCV activity into mod

OpenRA.Game/Traits/BaseBuilding.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRA.Traits
+{
+	/* tag trait for "bases": mcv/fact */
+	class BaseBuildingInfo : TraitInfo<BaseBuilding> { }
+	class BaseBuilding { }
+}