Rolls-Royce now joins a number of other ultra-luxury carmakers, including Bentley and Porsche, that will work with a limited number of wealthy clients to build very expensive customized cars. (Both Bentley and Porsche are owned by the Volkswagen Group, while Rolls-Royce is owned by BMW.) On Thursday, Rolls-Royce revealed a new program called Rolls-Royce Coachbuild. This department will work with individual clients to help design and build cars specifically for them.The luxury automaker will work on just one of these