[Feature] no-overlap with other jobs

[ashleysommer]

This is kind of related to #19, but the opposite.

Take for example I have two scheduled jobs. One running @hourly and one running @daily.
The @hourly job takes 1 minute to complete, every hour. The @daily one takes 45mins to complete, once per day.

I'd like a way to tell the @hourly job to not run if the @daily job is currently running. With either an option to just skip this hour, or alternatively schedule it to start running as soon as the @daily job is done.

This seems like an ambitious feature request.

[ashleysommer]

I know this can be done on the application level. Where I can program the app to use a lock file or something such that the hourly job knows that the daily job is running.
But I think this would be a useful built-in feature in ofelia.