Meals begin at the cashier's station where meal plan holders' cards are swiped and all others pay cash or use the Gull Card or Dining Dollars.    The concourse leads to the airy Rotunda, whose centerpiece is a bronze statue on a granite pedestal. She is Diana, Roman goddess of the hunt, crafted in this pose by Augustus Saint-Gaudens in 1873. Dining rooms and the two serving areas, the Marketplace and the Bistro, open onto the Rotunda's first floor, called the Courtyard, which features cafe seating.      View 3D Movie (requires Apple's QuickTime)   The surroundings are classic and elegant, and the meals have to measure up. It's no longer enough just to put food in front of students and expect them to eat it. We want to exceed their expectations, continuing the good experience they are enjoying outside our doors.  We serve people, not food.