Author: Petr Škoda
MDL-23875 improve cohort only help
Credit goes to Helen Foster.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=af29ef049e4f4e6b606a41b06ef306fcbc101ea3
http://github.com/moodle/moodle/commit/af29ef049e4f4e6b606a41b06ef306fcbc101ea3
+ 2.4 en [cohortonly_help,enrol_self]