submodule bug fix & Clip extend

移除submodule重复引用的问题，
Clip现在可以保存任意GameElement，且任意指定物体作为父物体加载

Assets/Scripts/DynamicUI/Inspector/IHaveInspection.cs

@@ -56,7 +56,7 @@ namespace Ichni.Editor
             DynamicUIButton button = Object.Instantiate(EditorManager.instance.basePrefabs.button, container.rect)
                 .GetComponent<DynamicUIButton>();
             button.SetText(buttonText, title != "null");
-            button.Initialize(baseElement, title, "null");
+            button.Initialize(baseElement, title, string.Empty);
             button.ApplyFunction(function);
             container.dynamicUIElements.Add(button);
             return button;