LPS-46151

Heya Bruno, there are a couple of issues still. I'm sending you this pull because I took care of one of the biggest ones, which is to separate the skin and structure like we do in other taglibs. Here are the remaining issues:
1. Can you remove the Classic specific colors and place them into custom_common inside of Classic? It should still be usable without any custom.css (so for the taglib css choose neutral colors, like #333 for the selected background color) and for the box-shadows and border-radius for the numbers move those into custom_common as well.
2. The other major thing that's keeping me back from passing this on is that it's really janky on mobile. We should be approaching this mobile first, but this appears to be our typical process of thinking about mobile after the fact. I don't know if this piece needs to go back to Juan H, but can you guys coordinate that before resending? Thanks Bruno!