Enrolment and auth plugins need following features:
- progress trace redirection to buffer so that results may be mailed to admins
- error_log progress trace reporting
- redirection to multiple progress_trace instances
At present each enrol and auth plugin implements the $verbose CLI and cron output in a different way, that is bad and it needs to be improved. Solution is to slightly improve the standard progress_trace abstraction and use it in all enrolment and later auth plugins.