Active target

Mainly posting here for sanity-checking, review, comments. I don't expect this to get pulled in without some discussion of naming.

All components probably need some review to accommodate this change, though even I'm surprised how painlessly it's slipped into the component prototype chain so far.

Plenty of specs are failing, but that seems to be the case atop edge right now, I don't think this makes matters worse but wouldn't mind some double checking. (3283 specs/ 26 failing) I'm also not sure how this wil all play with the matte/digit work that's going on right now but I'd like this to be considered ahead of any of that.

I also might squash some parts of this change set before it's accepted but have left my work open for illustrative purposes.