Fixes lunch_by_day in classchange controller

See afa9fb6de33069679d5406869ae46541ed43a77e
Fix null graduation_year in classchanges

Make classchanges tolerant of null graduation_year values in student profiles

See 3d8f7e190428e510ec326859603b8a6ef04b3e36
Fixes classchange comment
Fixes priorityLimit()