Author: Shamim Rezaie
MDL-69166 enrol_fee: set a description for enrolment
http://git.moodle.org/gw?p=moodle.git;a=commit;h=e88e3b87be7ad6ec01bacba79bfb79fcff2c5e94
http://github.com/moodle/moodle/commit/e88e3b87be7ad6ec01bacba79bfb79fcff2c5e94
+ 4.0 en [purchasedescription,enrol_fee]