The lofty new modern art museum in Munich boasts a world-class collection of art, design, and architecture. But on May 19, the specially invited guests weren't there to gawk at the Picassos and Mirós. They were assembled to appraise the art Bavarians love best: The latest model from Bayerische Motoren Werke. More than 100 German car dealers crowded around the revamped 5 Series sedan, the heart of