By Leah Schnurr NEW YORK (Reuters) - Wall Street was set for a weaker open on Friday, pulling back from record levels set a day earlier, after retail sales unexpectedly dropped last month and as results from major banks failed to impress investors. Futures extended losses after data showed retail sales fell 0.4 percent in March, while February's strong gain was revised down slightly. Consumer spending plays a key role in the U.S. economy, accounting for two-thirds of activity. ...