Fix an error, the peerreview was not evaluated rigthly:

https://github.com/OpenMOOC/moocng/blob/405b18dfafd2d94ef2b1e8340b85bfd447d596f1/moocng/courses/marks.py#L47

And I refactored the code. I have gotten a easier solution than the current, and with the same features. I removed "use_in_total" of the code

It's possible that the refactor is incomplete

Removed the marks old view