Sensei: Sorting does not work for learners on the Analysis page

[jenhooks]

On the Sensei > Analysis page, sorting by Active Courses doesn't work (GIF below):

To reproduce:

1. Create a few test learners and add them to a varying number of courses under Sensei > Learner Management.
2. Go to Sensei > Analysis, and try to sort by Active Courses.

Reported in 1027928-zen

[donnapep]

Note that sorting by _Active Courses_, _Completed Courses_ or _Average Grade_ does not work. Sorting currently only works on the _Learner_ and _Date Registered_ columns.

[amroland]

Sorting also does not work on the other tabs (_Courses_ and _Lessons_).

[jenhooks]

1283566-zen

[peterhebert]

The column sorting also does not work on the Sensei > Grading page. Does not work with any of the column headers ( Learner | Course | Lesson | Updated | Status | Grade )

[danjjohnson]

2509193-zen

[donnapep]

Note that the scope of this PR should be limited to the _Active Courses_, _Completed Courses_ and _Average Grade_ columns on the _Analysis_ > _Learners_ page only.