Undo delete restores boxes in the wrong order (#83)
In a class diagram, I had a Package containing 1 Class with 2 sub-Classes.
I deleted the Package, which automatically deleted the Classes too. (Strangely, the Generalization arrows were not deleted). Then, I clicked "Undo" to restore them.
Unfortunately, the Classes were now hidden below the Package.
When Undo-ing, the Classes should be restored above the Package.