add course id
Added a status message to user if update of students failed
[2709]adminSessions: show course ID

fixes #2709
Changed status message
Set error status when exception is detected
Added severe log message when exception is detected when updating student
Merge branch 'master' into Issue2683
[2683] Exception thrown unexpectedly while enrolling student
Fixed bug where average excluding self response column was wrong if user did not give himself a score
Fixed incorrect header names in csv
Refactored code
Merge branch 'master' into Issue2658