Revision 2343

Updated ProblemSetList.pm to import gateway or versioned assignments
from set.def files (which means that it's not necessary to manually
edit these parameters in the database--woo woo!).  New fields admitted
in set.def files are
  assignmentType      = gateway
  attemptsPerVersion  = \d+
  timeInterval        = \d+ unit (e.g., 1 day, 12 hours, or 6 hr)
  versionsPerInterval = \d+
  versionTimeLimit    = \d+ unit
  problemRandOrder    = 1
all of these are, by default, NULL.  It may be that we should promote
them to '' instead.

I haven't added the ability to edit these values on the SetList page.
Putting all of them in the set data table will make it unwieldy, I
think.