Fold “Touching” opacity changes into the Opacity expression

[swizzlevixen]

The whole reason the FingerTouch highlight is a subcomp is historical, because the highlight used to be two images — one convex, one concave — that swapped out during the touch event. Now that we're only doing an opacity change, it should be reasonable to fold that into the opacity expression, and eliminate the need for subcomps, and all the string matching shenanigans that entails.