Batch delete PyTA annotations

[donny-wong]

Context:
When PyTA is run with annotations enabled, it automatically adds its own annotations. However, rerunning the tests again, PyTA will continue to add annotations, which can lead to duplications of its own annotations.

Currently to remove duplicate annotations, we can either re-collect all submissions or manually go into each submission to delete them. When manually deleting them, you can go into the grading view of a submission, under the annotations tab, you will have the option to delete the annotations one at a time.

Proposed solution:
Manual deletion: we can have a "select all" check box, and individual checkbox next to each annotation item, where we can select all or the ones we want, and then have a button to delete them, located somewhere on the top.

Mass deletion: an idea is to have a button on the submissions table page to automatically delete all default annotations for the selected submissions.