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.
To add a bit more clarity. The ring size is the number of ensembles in the cluster. Each ensemble gets a part of the keyspace (2^160/Ring Size). Increasing the ring size reduces the portion of the keyspace each ensemble is responsible for. However, if if there are small number of physical nodes and a large number of vnodes, more ensembles will be affected if a node crashes because their vnodes (and corresponding peers) are likely to be on that same crashed node. If we add nodes, the vnodes spread out and this reduces the probability that any crashed node affects a large number of ensembles availability. Therefore, for a fixed ensemble size, increasing the number of physical nodes reduces the likely size of the affected portion of the keyspace. However, Increasing the number of nodes so that there are less vnodes/node however can limit concurrency on that node and underutilize it. Therefore we recommend typically to approximately have around 10 vnodes/node. There are more specific details somewhere in the docs I think. Because you can never have exactly 10, and diff HW has diff capabilities. Also, if you have n-disks on one physical node and vnodes are writing to diff disks, or raid is used the failure rates change, and so does performance. Best we can do is make recommendations and say "try it and tune it".