Make full use of title attributes in the gradebook

This small change would make the gradebook lots more usable, especially when two assessments have similar names. I'm not sure if an overlib pop-up would be better as it could then show the title of the assessment and also the instructions. Especially useful for essays where you can't remember the question you set and don't want to lose all your gradebook row highlighting just to go and check.

This makes a difference mainly to novice teachers who are not yet aware of the implications of long assessment titles in the gradebook.