(WIP) Class diagram transfer

A start at transferring content from the class diagram into code.  Focuses on School/Course/Klass/Educator/Student type models.  

@Dantemss I'd appreciate a once over of this PR if you have a chance.
Educators are (at least currently) only for Klasses.  We don't link Educators to specific Sections, so I don't know if we need a separate join table.