Issue #1493098 by sun, jcisio, pcambra, Pol, wamilton, Rok Žlender, beejeebus: convert cron settings to configuration system.

PR for https://github.com/backdrop/backdrop-issues/issues/170
We can remove this chunk, as it doesn't do anything. Sorry the contact module example may have included it, but it should have been removed later (if it hasn't been already).