Populate prioritySelection only for phase 2
Clear dirty bits only if we're about to update the server
Extend class_subjects json view

Add a new sub-view, class_subjects/catalog, which includes
description, prerequisites, and difficulty. Also adds category id in
addition to the category symbol.
Use category id as key for filtering rather than category symbol
Extend sections JSON view

Add a /catalog subview that includes meeting time and capacity.
Add section time and enrollment information to catalog