WANT to be a billionaire? It's simple. "Just sell roast chicken," says Puspo Wardoyo, chuckling. The owner of Wong Solo, a network of restaurants now gaining popularity, he was not just joking. Born in Solo, Central Java, 46 years ago, he has proven his own words. With roast chicken as his specialty, he has opened 16 outlets with 1,000 employees in a number of major cities—Medan, Jakarta, Solo and Denpasar. His outlets, always