By Jason Lange WASHINGTON (Reuters) - Retail sales contracted in March for the second time in three months, a sign the American economy may have stumbled at the end of the first quarter. Retail sales fell 0.4 percent during the month, the Commerce Department said on Friday. That was below analysts' expectations that sales would be flat. The sales data supports the view that the U.S. economy continues to struggle and hasn't gained as much momentum has analysts believed just a few weeks ago. ...