Sections covers "weeks", "topics" and anything else that may come along.
Note, again, some databases have changed esp course_weeks -> course_sections
and several fields called "week" are now "section. Also course no longer
has an enddate, but instead has a numsections field.
except it isn't constrained by times. Useful for flexible courses
where the pace isn't known and is subject to change. The teacher
can "mark" the current topic and change this marking as necessary.
