Add a config setting for storing application settings

Summary:
I'm just going to store application policy settings (like view/edit policy, and default policies for content) in config, because:

  1) We'll need access to it on every page, and Config is "free" since we already pull it.
  2) Building separate storage and transactions seems like overkill, we get less-nice but pretty-reasonable transactions for free with config.
  3) We could easily move it later if this is a bad call.

Also fix some formatting.

Test Plan: See future revisions.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7202