Add new trait interface INotifyTransformed and use it in Allies 04 to make the transport remove its cargo capacity after it unloads its passengers

OpenRA.Mods.RA/TraitsInterfaces.cs

@@ -45,4 +45,5 @@ namespace OpenRA.Mods.RA
 
 	public interface INotifyParachuteLanded { void OnLanded(); }
 	public interface INotifyTransform { void OnTransform(Actor self); }
+	public interface INotifyTransformed { void OnTransformed(Actor toActor); }
 }