Cooldown / Backoff for failure notifications

[dustinaja]

Currently failing devices notify every 5x run interval. This can be disabled or set to a different interval (although poorly documented). It might be nice to have it cool off to a longer period after a number of notifications have been sent.

https://github.com/aja-video/contra/blob/master/src/collectors/collectorworker.go#L133

https://github.com/aja-video/contra/blob/master/src/configuration/config_file.go#L31

[dustinaja]

I think I may give this a try. Thinking of trying to quiet it down to 1 per day if there have been more than 5 in the last 24 hours or thereabouts. Seem reasonable @slarti5191 ?