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
trimming and lowercasing for importing and editing
revert previous commit 'sort case insensitive'
readded the import and new user buttons on the users page which were unintentionally removed
fixed tests
Merge pull request #384 from janno42/trimming

Trimming
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
added warning for results with few answers
changed when and where warning is shown
translations
removed comments; refactored elifs
refactoring warning calculation
don't show warning if no answers were given