[Test Case] Instructor imports roster

[victorhuangwq]

1. Instructor should log in, go into manage autolab, then manage users
2. Upload a roster
3. The new students should show up
4. The changes made should be highlighted correctly
5. Upload a new roster, with new students, dropped students
6. The changes made should be highlighted correctly.
7. Add course assistants using the dropdown "Add Users from Email"
8. Instructor can change a student into a course assistant