Add an option to switch back to the old Scaleform UI

I personally dislike the way the current CEF UI looks right now and I think some others would agree. I know that it might become better in the future but I wouldn’t see much harm in keeping the old UI available as well.

Some toggle in the Options menu would be nice.

I do understand the old UI will eventually be outdated and no longer supported, but by then the CEF UI might have had more time to be refined.