Poll/refresh saved searches periodically

[cespare]

In keeping with the email paradigm, it would be good if we would periodically poll the server for changes so you can keep barkeep open indefinitely and see new commits as they come in.

An easy first pass attempt here would just be to call refreshAllSearches (or whatever it's called) every few minutes. This will show the refresh in the UI, however -- it might be nicer to do it silently.