List of changes:
* configurable unenrol action
* new setting for synchronisation of all enrolled users or users with at least one role
* cron period increased to 1 hour in order to lower server load, courses should not get out of sync often
* CLI sync script for debugging or manual sync
* phpdocs fixes
* when plugin is disabled all roles are removed, enrollments are kept
* uninstall script
* other bugfixing