Cleans up student reg phase 2 view

This is still a work in progress. I will work on setting up the
timeslot-specific view first, then tie it all together with the
overall phase2 view.
Creates a working timeslot_priorities view

This is based on the existing catalog template. Includes a few JS
tweaks to make this happen.
Adds Select2 JS library
Converts phase2 dropdowns to Select2