Automatically update routes list

[nigeldeakin]

If a specific app is being displayed, and a new route is then created (or an existing route is then deleted) using the CLI (or perhaps another UI window) then the list of routes remains unchanged. The list of routes is not updated until the page is refreshed.

This is inconsistent with the behaviour of the graphs on this page, which will automatically update themselves if a new route is added and then called.

The page should automatically detect that a new route has been created (or deleted) and update the display accordingly. We already have a background thread fetching stats, so it is not unreasonable to also have a background thread fetching a list of routes. The thread should probably run only whilst the app in question was being displayed.

[nigeldeakin]

See also #41, which describes the same issue for the top-level apps list.