New Role: CourseRoleSuper. Server admin can access any course level command.

[Lucas-Ellenberger]

This PR adds a new role 'CourseRoleSuper' which cannot be held by a normal user within a course (it will be a validation error). The role is reserved for users with serverRoleAdmin or above that are using course specific APIs. These server admins are granted a higher role to have power over the courseRoleOwner role. This distinction is important for actions that cannot be performed against users with an equal role (like the future courses/users/drop).

[Lucas-Ellenberger]

The following APIs need more test cases:

CourseUserContext:

• admin/logs_fetch.go
• admin/update_course
• lms/user_get
• lms/upload_scores
• courses/assignments/list

AssignmentContext:

• submissions/fetch_scores
• submissions/fetch_submissions
• submissions/submit
• submissions/remove_submissions
• submissions/peek
• submissions/fetch_submissions
• submissions/history
• submissions/fetch_attempts
• courses/assignments/get

The list of APIs will change following the refactoring of these APIs and their packages. There will be new APIs that will need tests as well. After expanding the test data, I will need to update a lot of test cases to work properly.