Author: Tim Hunt
MDL-42125 quiz stats: clearer message when manual grading required
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3ab94015bb5be66fcebde49205f5167398e9e15f
http://github.com/moodle/moodle/commit/3ab94015bb5be66fcebde49205f5167398e9e15f
+ 3.0 en [nogradedattempts,quiz_statistics]