Author: Paul Holden
MDL-75349 group: implement groups datasource for custom reporting.
Create new entities for exposing report data on course groups and
groupings, joining to existing course/user entities to provide data
for the reportbuilder editor.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=b10b89ec74ea84bedb479f5d0a288a6dd95345cc
http://github.com/moodle/moodle/commit/b10b89ec74ea84bedb479f5d0a288a6dd95345cc
+ 4.1 en [picture,core]