Sync is now automatically triggered by add/update instance. We need
to manually trigger sync before each part of the test to clean up
role assignments from the previous test.
This patch includes following changes and new features:
* Group sync in enrol_cohort plugin.
* Option for editing of role in existing cohort sync instance.
* Group memberships are now restored after enrolments.
* New enrol method for restore of protected group membership.
* New component callback 'restore_group_member' for restore of general plugin group membership.
* New component callback 'restore_role_assignment' for restore of general plugin role assignments.
* Implemented group membership protection in enrolment UI.
* Other minor fixes and cleanup.
Notes:
* The YUI base enrolment page is not reimplemented yet - see MDL-35618.