Required Grading bug fix

Fixed bug where students would still have to grade an exam even if the
teacher set the global number to grade setting to 0.
Got rid of reviewing, made timers work across timezones.
View past exams
View past exams
Send confirmation email
Login to access student content
AbstractUserStudent
Changed Exam to use secure login
Clicker signin and bug fixes

Made clicker sign in work with the global signin, fixed bug where
redirection didn't work, fixed bug where
BioExamBundle:Public:main.html.twig didn't extend a real file.
Score finding update

Made score finding do global login, updated how scores are displayed.
Field trip update
Switch Sections
Cleanup
Merge branch 'better-login' into exam-improvements
Merge branch 'exam-improvements'