Author: Shamim Rezaie
MDL-66360 core_grade: New method to send grade notifications to students
http://git.moodle.org/gw?p=moodle.git;a=commit;h=9672c8aa081b434ff42f6a3c2b1f3f2eb81d62b8
http://github.com/moodle/moodle/commit/9672c8aa081b434ff42f6a3c2b1f3f2eb81d62b8
+ 3.8 en [gradenotificationmessage,core_grades]
+ 3.8 en [gradenotificationsubject,core_grades]