Author: Damyon Wiese
MDL-48634 grades: Make the rescaling option required if maxgrade changes
http://git.moodle.org/gw?p=moodle.git;a=commit;h=e7c71c189bb906741951e69c8c178191bf81bf3c
http://github.com/moodle/moodle/commit/e7c71c189bb906741951e69c8c178191bf81bf3c
+ 3.1 en [mustchooserescaleyesorno,core_grades]