Author: Huong Nguyen
MDL-79809 environment: Add recommended custom check
Add support for custom environment checks to have a recommended
option in addition to required an optional.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=2978ffc4a5079fa1eda93474e978eb90a0e8d820
http://github.com/moodle/moodle/commit/2978ffc4a5079fa1eda93474e978eb90a0e8d820
+ 4.1 en [environmentshouldfixcustomcheck,core_admin]