Master

Most of this stuff is for the pip2 textbook, which you may or may not want to take (yet).

But the 89ab321 commit I think is very useful right now. It creates progress records as they are needed. This is helpful for users who pre-existed, and also if new chapters or subchapters are ever added to a book in mid-course. I also inserted one comment that I think may be identifying a potential bug that will only manfiest later. Feel free to delete that comment if I'm wrong about the possible bug.

The last two commits are for lti integration. It came out much cleaner with the integration.