Major changes throughout to change "week" notation to "section" notation.

Major changes throughout to change "week" notation to "section" notation.
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.