reduced size of user_exam table + hoverzoom fix

- by only inserting values for users who have specific settings
- as a result redid studentsSearchService to use a huge 72 line query
to determine the user's exam status and be able to sort by it (it was
stored in user_exam before for every student)
Merge branch 'master' of https://github.com/lorencs/Ualberta-Assessment-Tool-Prototype

Conflicts:
	exam.php