Translation correction
rename GradeAnswer to LikertAnswer
adding GradeAnswer and redefining total grade calculation
redefine migration, added missing settings
adapting test_data and completing translations
fixing vote_test
Merge pull request #349 from janno42/summary_grade

LikertAnswer/GradeAnswer
updated infoboxes
enabled result preview for staff (fsr members)
singular/plural fixes; removed unnecessary staff test
Merge pull request #353 from janno42/result_preview

enabled result preview for staff (fsr members)
changed color of comment review button in fsr view
added overview to results_course_detail page
fixed indent
Merge pull request #354 from janno42/master

added overview to results_course_detail page
added user import
show message when a course has not enough participants to publish its results
importer refactoring
Merge pull request #358 from janno42/highlight_courses

Show warning when not enough participants
Update django.po