follow activity for turreted attacks

OpenRa.Game/Traits/Activities/IActivity.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRa.Game.Traits.Activities
+{
+	interface IActivity
+	{
+		IActivity NextActivity { get; set; }
+		void Tick( Actor self, Mobile mobile );
+		void Cancel( Actor self, Mobile mobile );
+	}
+}