Export Service Improvements

Hints only shown if hints present in exam. Says N/A if no hints
available for that item. Shows 0 if hints available but none used for
an item. Exam export shows list of incorrectly answered questions.
Merge branch 'master' of https://github.com/lorencs/Ualberta-Assessment-Tool-Prototype

Conflicts:
	php/profFuncs.php