Option to disable assessments for students

[jlge]

Feature request from 17-681

Currently TAs and instructors grade the final using an assessment on Autolab, but in order to hide the assessment from students they need to manually set the end date of the assignment. It would be nice to be able to set the assessment as TA/instructor only.

[20wildmanj]

Option to disable explicitly through a toggle instead of having to set date.