Bug 6239 - Allow questions to have some teacher-supplied commentary.

Bug 6239 - Allow questions to have some teacher-supplied commentary.

While implementing this, I removed the ~100 lines of very similar code from the top of each question type's editquestion.html template, and moved this to a the function print_question_form_start() in the base class, which uses the template question/type/editquestionstart.html. This is described in more detail here: http://moodle.org/mod/forum/discuss.php?d=51590, and is why this patch makes the codebase 523 lines smaller.