Live update multiple servers

This pull request allows the live radiator view to show jobs from multiple servers, rather than the hardcoded jenkins-foss server.
I think a default `refresh_interval` of 10 might be a bit too fast. With the amount of time it takes Jenkins to respond to API calls, this might start stacking up. Perhaps bump this default (fallback) to 30, and then set `refresh_interval` to 10 in `waylon.yml` to see how it behaves. Unless you've already tried that, of course.