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.
In the case of 3 replicas, if one is down it still makes quorum. Additionally the scenarios below are inaccurate. The issue is that the number of ensembles is equal to the ring size. Each ensemble's peers and vnodes are then layed out according to the ring plan. So for a 50 node cluster, with a ring size of 512, you'd have approximately 10 vnodes per node, although some may have more, while some less. If target_n_val is set appropriately than each vnode for a given ensemble will be on a diff physical node. With N=5, each vnode will handle data for 5 replicas from neighboring partitions. Therefore we will end up touching about 50 of the 512 ensembles, which in this case happens to be 10%. However, if we were to use a ring size of only 64, we'd end up with 1-2 vnodes/ node and thus would affect 5 - 10 of the 64 ensembles with N=5. Therefore a failure of a single node in this case impacts 7-15% of ensembles. The key point to take away is that these numbers are not based on cluster size and n_val alone, and are often imprecise because they must take into account the number of nodes, the ring size, the n_val and the current cluster plan. Creating a 50 node cluster once results in a different vnode layout than adding nodes periodically until you eventually hit 50. I know this makes things harder to describe, but it's too late for me to come up with a clear way to put it right now.