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.
You're right, that needs to be better written. I was trying to leave in your point about larger clusters. The issue isn't really with the size of the cluster as much as the ratio of vnodes/nodes and the fact that the you need at least target_n_val nodes for each vnode to be on it's own separate node. We typically recommend not having more than 10 vnodes / node. So with ring size of 128, you'd want about 12 nodes etc...