Add logic to answer and evaluate buttons on course and question screens:

- answer shown when user has not answered and the answer period is active OR the user is an instructor
- answered shown when user has answered and the answer period is active OR the user is an instructor
- evaluate shown when user is not an instructor, the judging period is active, and evaluations are remaining
- evaluated shown when user is not an instructor, the judging period is active and no evaluations remain

Display different blank states for answers when not answered or not judged.

Hide answers until user has answered and judged.