Clean up styles

I've begun the work of making the implementation of style methods more uniform and correct, but this got to be so big that I decided to stop half-way.

This PR will represent "cleaning up" `arc` - `list_box` (using the list in #711).

I'll make lots of inline comments on what I considered "cleaning" and I'm eager to hear feedback.
I moved initialization of `items` and `choose` over to the gui because in general I think we want the gui to initialize itself and then wait for the dsl to make changes. . . but I don't have a strong preference.