* porting and port testing
* add "refresh" buttons? (or refresh automatically?)
* rescan before committing.  mark each entry as to-be-deleted, to-be-added,
  or unchanged, and apply the changes appropriately while rescanning.
* preserve comments/spacing in cron files? (nah)
* add some way to kill launched jobs (separate helper program?)
* (better) validators in the druids
* zero-pad the minute spinners.  Does this mean abandoning GtkSpinButton?
* add AM/PM to hour spinners
* check for memory and file descriptor leaks
* add special classes of jobs like "send an e-mail" or "pop up a message"
