Patch to Copy/Duplicate scenes

Hi,

I decided to add a way to copy Scenes. So that you can use a base scene that you don't have to recreate and reconfigure in its entirety just to make minor changes.

I tried to keep the style the same, but it's not much code anyway. Had to add functions to XConfig unfortunately, copy functions did not seem to exist yet.

The Copy menu item is basically a copy-paste of the Add menu item, but with a function call to copy the subitems from the selected scene.

I added locale texts for EN and NL, but I dared not reach for google translate to add the other translations.