Can view and submit a task that has been completed

[hltcoe-bot]

1. Create project and batch. 1 assignment per task.
2. Complete the task
3. Press the back button

You will see the task again and I think be able to submit it again. I assume it overwrites the previous submission. I haven't done much testing with this, but I could see annotators using the back button accidentally. You can also view tasks that have been completed with the direct URL like http://localhost:8000/turkle/task/5/assignment/7/

Poster: Cash Costello id: 130

[hltcoe-bot]

mentioned in merge request !195

Poster: Craig Harman

[hltcoe-bot]

mentioned in issue #251

Poster: Craig Harman