Add instructors

[maddiedierker]

Similar to the way TAs can view their history and sign up for classes, instructors should be able to have a record of their teaching history. TAMS admins should add the instructor to the class at the time the course is added to the system.

We should also use TAMS to track instructors' teaching interests and contact information.

Note: We already enter class info to attach TAs to classes. Do we have an existing Class table that we can also use to attach Instructors to these classes?