Changes 13-01-13 @ 23:

> Edited `seatdisplay::seatbooking()` so that it does not show the
dialogue for entering details if a customer is already looged in. Has
not been completed as it doesn't actually book the chosen seats.
> Edited `seatdisplay::disableBooked()` as the new column in `bookings`
is called "ID" not "Event_ID"
> Deleted O[58] in "seatdisplay.h"