Economist: WHATEVER the travails of the Greek economy, George Papandreou has a gift for accentuating the positive. Ask the prime minister about his country’s comparative advantages, and he is likely to mention the health benefits of the Mediterranean diet. His latest paean on the subject, at a resort south of Athens on October 22nd, had a sympathetic audience: a grouping of Mediterranean politicians, including Israelis, Palestinians, Greek-Cypriots and Turks, who probably found it easier to agree on culinary…