Is your feature request related to a problem? Please describe.

Maintaining JobQueue is not easy and sometimes error prone, see e.g. #1338

Describe the solution you'd like

We could refactor JobQueue to use a third party library for the scheduling, keeping the run_* methods as wrappers. We should probably also add a run_cron as suggested in #1337 as convenience wrapper for all the other cases we can't all cover (like run a job every time mars and saturn align …)

Describe alternatives you've considered

Just implement run_cron would be a first step.