Reset per-job limits#688

I need to set restrictions on per-job print times. I do not want students printing jobs over 3 hours, unless they have prior clearance from me. Instead of setting a hard per-job limit, using the Quotas and Limits section, I woud like a threshold trigger. Users should be able to make requests for more time, as they can currently do with material limits. These jobs could go into the Pending Approval section of the Print queue.