Author: Tim Hunt
MDL-42125 quiz stats: clearer message when manual grading required
http://git.moodle.org/gw?p=moodle.git;a=commit;h=ac32161ca64e40a13f4e4c81cca40f032483dea4
http://github.com/moodle/moodle/commit/ac32161ca64e40a13f4e4c81cca40f032483dea4
+ 3.1 en [nogradedattempts,quiz_statistics]