Setup teardown shifts

We now have rules in place for setup/teardown shifts.  Setup/teardown shifts will only be available to people who have been approved for setup/teardown rooms.  (Eventually we can and should have a separate process for approving people for setup/teardown who aren't getting hotel rooms, which is issue #672 and probably won't be done until next year.)

I still need to do #671 before we do printed schedules.