Auto-refresh button/form for scheduling checks

[willgearty]

suggestion from @benjaminjkraft based on a suggestion from @emannes: I think with the new scheduling checks page it would be fairly easy to just add an auto-refresh button (with suitable warnings, of course), and then we could have the normal checks page, open to the appropriate check, and with auto-refresh turned on, projected somewhere. Do people think that would be useful?

Originally posted by @benjaminjkraft in #1406 (comment)