Also did the following -
1. Changed get_grade_items() so it takes a course parameter.
2. Renamed get_grade() and get_mod_grade() and changed functionality
slightly to use newly introduced class.
3. Do not return a date graded value if there is no grade.
4. Added course grade date as an option to the date element.
5. Fix inconsistency between number of decimals showing for a grade
between the drag and drop interface and the PDF.
