Let badges be live-updatable via the CMS

[lazerwalker]

1. The list of badges should fetch from Redis instead of from disk files
2. The CMS should have a UI to edit the list of badges automatically granted to everyone

An open question is how we handle badges that are locked behind business logic (and thus require server code). My instinct is both the "free badges" and "unlockable badges" arrays can just be migrated to the CMS, with the understanding that code will still be required for unlockable badges.

My instinct is we can just migrate the existing JSON structures. Happy to advise on specific UI (e.g. where we let admins select badges in the CMS editor UI)

[lazerwalker]

See #820