Dashboard user interface

[jonnor]

We're accumulating a good set of tools around guv now, and these are mostly exposed as command-line utilities (see ./bin).
An interactive user interface may however make it easier to understand the system, and explore different possibilities.

There is some initial work in ./ui.

Major bonus points if the UI can be served as a webpage, so users do not have to install anything,
and connect to live production instances. Primarily for monitoring, but ideally also for changing/updating the active configuration.