Admin Panel

I'm starting in on a small web admin panel for editing AppContentSet. I'm not sure if this sort of functionality is still on the roadmap, but it'll be useful for @postcode on an upcoming deploy.

The idea here is to toss a little bit of code out there and talk about general application config. @daguar were talking about this yesterday and it seemed like things were up in the air with the approach. The roadmap talks about admin panes but #140 seems like @codeforamerica is taking a yml based approach.

No tests and this is all rebased off of some of the PR's that @ohrite submitted.