Author: Marina Glancy
MDL-44640 enrol: trigger events on instances actions
http://git.moodle.org/gw?p=moodle.git;a=commit;h=080c7d471de81bb1ef0ac3e1a56f39a6a15c2a43
http://github.com/moodle/moodle/commit/080c7d471de81bb1ef0ac3e1a56f39a6a15c2a43
+ 3.0 en [eventenrolinstancecreated,core_enrol]
+ 3.0 en [eventenrolinstancedeleted,core_enrol]
+ 3.0 en [eventenrolinstanceupdated,core_enrol]