Removed an unused method
Added full coverage for 2 functions. Changed a TestHelper function to expand its flexibility
Cleaned up StudentFeedbackResultsPageActionTest
created a new test file to cover the FRCDb completely. Added a few data to the typical bundle for better coverage
deleted comments
Added test to check for null Google ID during instructor course join

Test to check that new instructors institutes are set correctly even if
some instructors in the course have null Google IDs.
[1997] Cleaned up StudentFeedbackResultsPageAction

fixes #1997
Merge branch 'master' into Issue1817
[1817] InstructorCourseJoin: parameter becomes null although it was checked for null before

fixes #1817
[1990] Clean up StudentDbTest

fixes #1990
Merge branch 'master' of https://github.com/TEAMMATES/repo into Issue1989
[1989] Clean up FeedbackResponseCommentsDb

fixes #1989
Merge remote-tracking branch 'origin/master' into Issue1949