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