Merge dynamic reviewer assignment functionality from projectA branch about expertiza

[nilbus]

I've applied the OSS E7 code to the production server after fixing things up and making it work.

Some things were really wrong, and it makes me wonder if they ever even got it working enough to test it in the browser. Anyway, I fixed a few typos, and it seems to work reasonably well now.

It is not yet fully implemented. When choosing a submission, it doesn't ensure that you haven't already reviewed that submission, or a few other things that it should check. However, it doesn't blow up or anything. I think it's stable enough to have on production for you to test.

To use it:

• edit/create an assignment, and check the box labeled "Use dynamic reviewers for this assignment"
• assign some students to the assignment
• impersonate a student and submit some work
• impersonate another student and request to review work

I also applied all the fixes to branches projectA and projectB for them to work with as they complete their final project.