Shows class-hours by category on the dashboard
Adds "Grades" section on the dashboard, which shows students per grade
and number of subjects/sections available to each grade.

It still should probably be optimized better, and students per grade
currently doesn't work for programs before the current year.
Shows additional info in dashboard status popup
Changes getGrade(program) to return the grade the student was in when that program ran
Moves some logic out of getGrade() into other methods
Fixes sections attribute in class_admin_info()
Fixes query for grade_sections
Removes obsolete comment
Removes _grade property because it's unnecessary
Merge pull request #892 from learning-unlimited/mgersh-dashboard

More data on the dashboard: #733, #842, #854