changed student index page layout and functionality
changed menu
updating layout of the lecturers page following the layout of the new students page
update rating colors
refactoring
changed course sorting for students
Merge pull request #377 from janno42/new_student_page

New student page
Merge pull request #378 from janno42/new_lecturer_page

Updating layout of the lecturers page
Merge pull request #383 from janno42/update_colors

Update rating colors