py: grand st3m unification

Commandeering @iggy 's stemming_merge branch and continuing his work.

This is now at the point where we fully moved st4m back into st3m, and we have the ability to launch applications from the new 'sun' menu.

I had to undo some changes that I hope to restore soon:

1. Captouch-based scroll. It still lives in comments.
2. The old flower-menu but rebuilt on top of the new menu/scroll framework.

But this at least brings us one step closer to production code, and unblocks a bunch of other stuff.