some fixes in quiz + end version of big test!
Merge branch 'master' of https://github.com/kontur-edu/uLearn
evaluation of the quality of the material is removed when you press button again
correct slide-navigation logic + minor changes in slides
Merge branch 'master' of https://github.com/kontur-edu/uLearn
many things for Ivan
Merge branch 'master' of https://github.com/kontur-edu/uLearn