Re-implement relative motion.

Assets/Cryville/Crtr/Event/ContainerHandler.cs

@@ -203,6 +203,7 @@ namespace Cryville.Crtr.Event {
 		}
 		#endregion
 		#region Anchor
+		public virtual void PreAnchor() { }
 		public virtual void Anchor() {
 			foreach (var p in PropSrcs) p.Value.Invalidate();
 			foreach (var a in DynamicAnchors) DynamicAnchorSetTime[a.Key] = double.NaN;