Bankruptcy is supposed to be bad for a business. Yet some jewelers say bankruptcy reorganization was the best thing that could have happened to them. Samuel J. Merksamer, president of Merksamer Jewelers, even suggests that those who haven't gone through one may have a competitive disadvantage in the 1990s. "Those of us who have downsized and reorganized are leaner and more focused" on customers, business and profitability, he says. Certainly no one advocates bankruptcy restructuring as standard operating procedure. But any jeweler can benefit by imitating the requirements of bankruptcy reorganization - taking a hard look at operations and costs in order to cut deadwood and fat, upgrade systems and modify marketing to stay profitable. Glennpeter Jewelers on the East Coast and Barry's Jewelers and Merksamer Jewelers on the West Coast are examples of businesses that were forced to ree