remove unused code
random minor cleanups and fixes
give the ReviewTextAnswerForm a model so it's better testable
fix semesters being always deletable
lottery: only include courses that users had a chance to evaluate
rename edited_answer to reviewed_answer, and a small refactoring
prevent contributors from previewing other courses
guard student pages with a new @enrolment_required. redirect all the people to /results if they accessed wrong pages.
fix a wrong div in a template. it made my tests crash
if user cannot see the results of a course, give him a 403.
Merge pull request #426 from karyon/lots_of_random_things

Lots of random things