Armed with newly minted tourist visas, Chinese visitors are coming to America in search of luxury goods. Prepare yourself for the decade’s biggest marketing opportunity.Several years ago, Julie Sather-Browne, vice president of ­Sather’s Leading Jewelers in Fort Collins, Colo., was approached by the manager of a local water-purification consulting firm with a significant presence in China. The executive had a slew of Chinese visitors coming to town who wanted to take back gold and diamond jewelry as souvenirs, and was hoping to arrange a group buying trip to Sather’s.The retailer, howeve