refactor *FeedbackResultsDownloadAction
clean up *feedbackResultsDownloadActionTest
optimize verifyAssumptionFailure logic
Revert "optimize verifyAssumptionFailure logic"

This reverts commit 14dbedfb9343c639aa25286e81c2bd23d4e085e4.
Merge branch 'master' into Issue1837
add fileName and fileContent tests to ensure it's downloadable
Merge branch 'master' into Issue1837
make dev green
[1837] Clean up InstructorFeedbackResultsDownloadAction

fixes #1837