Update classchange controller for schema modifications.
Update class changes email for Spring HSSP 2014.
Fix students not checked in query.
Fixes class changes form

Request StudentRegistrations were being created with an end_date of
9999-01-01, which is incorrect for ExpirableModles. Removes this
assignment, so that end_date is correctly set as None when new
registrations are created.
Merge pull request #1132 from learning-unlimited/classchanges_fixes

Classchanges fixes