Suspended user accounts should not have active enrollments in course

1. Create a course English
2. Enroll a student into the course (John A)
3. Go to user management (site administration) and suspend account John A
4. Go to participants in course English and see that John A is set as active in the course

You can debate about weather this is correct, John A has an 'active' enrollment in the course. But look at it from the teacher's perspective: students that have left the faculty are still visible as active members in his/her course English.

Several solutions are possible:

1. When user account is set to suspended, set enrolment status to inactive for all the courses
2. Unenroll suspended users from all courses
3. Add a tick box to the 'course participants' page that filters out suspended accounts
4. ???

The goal is quite simpel: make sure teachers don't see students that have left the faculty in the course participants page.