Author: Andrew Hancox
MDL-48451 report_outline: Added number of distinct users
http://git.moodle.org/gw?p=moodle.git;a=commit;h=30baca293b7bdb9aac7cda0b8c4ab510e38979e6
http://github.com/moodle/moodle/commit/30baca293b7bdb9aac7cda0b8c4ab510e38979e6
+ 3.1 en [numviews,report_outline]