Add tests for FeedbackSession Emails.
Change assertTrue(!...) to use assertFalse(...)
Rename verifyEvaluationEmail to verifyEmail, and use it to verify feedback session emails.
Remove unused, email related section in LogicTest
Remove unused imports and parameters.
Add FeedbackSessionEmailTaskQueueTest
Add the new test to testing.xml
Fix mistake in testing.xml
[1958] Clean up EmailsTest

fixes #1958
Merge branch 'master' of https://github.com/TEAMMATES/repo