Cluster management UI

@janl:
> Even without rebalancing, we need a nice Fauxton UI to manage the cluster, so far we only have a simple setup procedure (which is great don’t get me wrong), but users will want to do more elaborate cluster management and we should make that easy with a slick UI.

Start by reviewing Fauxton and the existing simple cluster setup procedure mentioned in the issue. Define the cluster-management workflows and UI scope before implementation; the issue does not identify files, tests, or a specific completion criterion.

Written by the indexing model from the issue text.