Rework brand and scar select

Been a while since I worked on these. Brand and scar selection overlap a lot, particularly when it come to selecting body parts. Made a common function for that.

Also, universal rules brand/scar selection overlaps a lot with slave brand/scar selection, so made their js functions wider in scope and more flexible so they could handle it.

The results should be more robust and easier to maintain, and are the next step in me converting universal rules to js.