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.
This is not true. In fact, on reads with leader leases enabled, 0 quorum round trips can be required from the leader (acting as coordinator) to it's followers and it can in fact have lower latency than the EC case of 1 round trip.

See the `Round Trips` section [here](https://github.com/basho/riak_ensemble/blob/wip/riak-2.0-user-docs/riak_consistent_user_docs.md)

Additionally, writes have increased latency because they also have to update the synctree on the leader before responding when `synchronous_tree_updates=false` and on update the synctree on a quorum of nodes with `synchronous_tree_updates=true`