Create Weave topology with info from the Weave router (or equivalent in another topology)

[tomwilkie]

So we can display the topology of weave router connections.

[tomwilkie]

This is pending #123.

I propose we add a new topology in the probe reports, which contains the weave nodes and their connections, and as much metadata as I can cleave out of weave. How does that sound?

[peterbourgon]

This is done, though we don't have connections. We can open another ticket for that. It would involve modifying the Weave router /status-json to expose that information, somehow.