Enchanced commenter class view

* For commenters with the locale language, show counts of all
  entries not yet commented in locale language.

* For commenters of other languages, show counts of all entries
  missed by students of that language that have been commented
  in the locale language, but are not yet commented in the
  student/commenter language.

This will want extending upward to the commenter top view,
and downward to the quiz mistakes view.