1.add a method to recover a html-sanitized string to original encoding
2.add a test for above method
3.call this method in instructorCourseStudentListDowloadAction to ensure the display is in correct format
change indentation
add test for student list downloading action with special team name
[2274]'/' in team name is messed up in the csv download

fixes #2274
Merge branch 'master' of https://github.com/TEAMMATES/repo