Revert 6762421..c988ada

This rolls back to commit 67624219a76b37056d92896c28fcbe68fb3494c6.
Revert c988ada..e41a672

This rolls back to commit c988adae96709a4a81329e53542c9d5bd78d387d.
Define the Relationships between Models...

Classes, Teacher, Students, and Appointments are related in ways that
might be meaningful in a school.