support duplicating components in editor

[WebFreak001]

Not too fixed on the current keyboard shortcuts (just pressing D, or Ctrl-D)

I'm not sure if I should be accessing the internals of the widget like I am doing here, or if I should abstract that away into some helper (if so and there is an existing one, I don't know which existing helper to put it in) - I needed to clear the internals like this to make sure that it doesn't have the same widget reference on multiple instances as well as in the saving that it didn't save the same reference twice (breaks rendering otherwise)

For rapidly creating a form with a few custom inputs this is a good time saver for me. Undo/redo support is something I would be quite interested in as well, but the code base didn't seem to be built for that yet and I would need a lot of time getting into the code.