Reduced Credit Date (develop)

Changed how the reduced credit checker works.  It now has a date provided to it by WeBWorK (rather than a reduced credit scoring period).  It just checks to see if time is after the reduced credit date to see if it applies reduced credit. 

This will break custom checkers that use the old logic.  However, its probably a better approach to have the graders provided a date and have the course management system decide how the date is defined.