It is China and the United States that prosper when power sets the terms for global commerce, says Peter Foster for the Financial Times. YAOUNDE, Cameroon: According to one account of his early career, Chinese minister of commerce Wang Wentao started out as the general manager of a photocopier sales department before ascending the ranks of China's Communist Party.  This week in the Cameroonian capital of Yaounde, where the 166-member World Trade Organization (WTO) had gathered , Wang was