Show when course is meta parent or child

[mwithheld]

If a course is an enrollment meta parent or child, admins need to consider that the course is empty because it's used solely for enrollments, and so admins may not want to delete them. E.g. child course collects enrolments, parent course is where students see the content.

I suggest adding flags like the 'MT' flag: X for meta, or XP and XC for meta parent and meta child.
And also adding the ability to filter those out on a search.

A course is a meta parent if it has more than one result from:
SELECT count(*)
FROM m_enrol e
WHERE enrol='meta'
AND e.courseid=[course id]

A course is a meta child if it has one or more results from:
SELECT count(*)
FROM m_enrol e
WHERE enrol='meta'
AND customint1=[course id]

[Syxton]

@mwithheld Not sure when I'll get to parsing this out as a separate identifier. I will say that the current "Empty" course description already takes into account meta course child. Since meta course children often don't have content. So if a blank course is a meta course child, it will not show up as "Empty" in the archiver.