Ready: Strong consistency update

- [x] Configs in `advanced.config`
- [x] `riak-admin` interface for ensemble
- [x] Implementation details

Heads up to @andrewjstone, @engelsanchez, and @jtuple when he's back.
I'd remove the 'preferably 7', unless @jtuple disagrees. Seems unnecessarily pessimistic. Pointing to the recommendations should be enough.