Basic renderhierarchy async updates

src/Engine/UI/System.h

@@ -0,0 +1,21 @@
+#pragma once
+#include "MinimalEngine.h"
+#include "RenderHierarchy.h"
+
+namespace Seele
+{
+namespace UI
+{
+DECLARE_REF(Panel)
+class System
+{
+public:
+    System();
+    virtual ~System();
+private:
+    PPanel rootPanel;
+    Array<RenderHierarchyUpdate*> updates;
+};
+DEFINE_REF(System)
+} // namespace UI
+} // namespace Seele