implement summary button

[sebkopf]

A button that can provide a summary of classes across the selected time frame (and search criteria!) with 3 categories:

service classes
majors classes
graduate classes

For each class listing, provide # semesters taught total + #semesters / AY + # sections taught total + # sections / academic year
For each category provide a sum entry at the end that sums these all together.

NOTE:
if selecting a faculty in the left, consider adding their teaching load information into the summary box too.