Provide a shareable assignment link in the BlockPy client

[acbart]

This would be for instructors to quickly get access to a students' submission. Students should ONLY be able to share their links with TAs and instructors; anyone else using the link will be given an "Access Denied" message (including the student themselves, to discourage accessing the link outside of canvas - unless we can redirect them to the embedded canvas version?).

Anyway, I want to provide a copy-able URL and a QR code. That way, instructors can just walk by with their phone and quickly scan it to reach the submission on BlockPy (and then launch a read-only view I guess).