Richard Stengel, a long-time writer and editor at Time magazine and the former head of its Web site, was named its managing editor yesterday, the 16th person to hold the job in the magazine's 83-year history. Mr. Stengel, 51, will oversee the newsweekly, which has a circulation of four million, and its Web site, Time.com, which draws more than three million unique visitors a month, a number that...