updating attendee no longer increments question_values_used. fixes #9
removes useless comment and unhides question_values_used in attendee registration form
rehauls question_values limits using hooks. strangely, only decrementing works, not incrementing. also reuses code into functions and makes sure question_values_used is never negative.

Signed-off-by: Basheer Subei <basheersubei@gmail.com>
question limit new attendee, trashing and untrashing works. Editing does not work (it increments one when it shouldn't)
question limit finally works! ugliest hacks and kludges used. USE WITH CAUTION.
ammar's js changes that take care of frontend stuff for workshops
enables attendance-track addon by hard-coding it in there
cleans up question_values code and adds comments