Author: Matt Davidson
MDL-68163 gradebook: add grade item duplication
http://git.moodle.org/gw?p=moodle.git;a=commit;h=887679e510590f3c6426806c90e180da284f78ef
http://github.com/moodle/moodle/commit/887679e510590f3c6426806c90e180da284f78ef
+ 3.9 en [duplicatedgradeitem,core_grades]