Author: Ryan Wyllie
MDL-57502 core_calendar: add calendar event exporters
Part of MDL-55611 epic.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=984355ce57bf130771755c9f95e96f2656588986
http://github.com/moodle/moodle/commit/984355ce57bf130771755c9f95e96f2656588986
+ 3.3 en [activityevent,core_calendar]