Add controls to the ActorToolbox in the GUI tab. Add dragging and dropping controls from toolbox into scene and prefab trees.

Source/Engine/UI/GUI/Common/Border.cs

@@ -5,6 +5,7 @@ namespace FlaxEngine.GUI
     /// <summary>
     /// Border control that draws the border around the control edges (inner and outer sides).
     /// </summary>
+    [ActorToolbox("GUI")]
     public class Border : ContainerControl
     {
         /// <summary>