Tooltips rework.

https://www.youtube.com/watch?v=Ug1r81Qg89U
The first constructor is unnecessary, because strings default to "".
The second constructor could probably be removed and {} used instead. (as in `TooltipSpec tts = {"Tooltip", SColor(1, 2, 3, 4), SColor(5, 6, 7, 8)};`, although it might not work).