(Reuters) - Toronto's main stock index looked set to open lower on Friday, mirroring its U.S. counterpart, following the release of unexpectedly soft U.S. retail sales data. TOP STORIES U.S. 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. Output at euro zone factories rose greater than expected in the month of February on a jump in energy production, a sign of growing demand giving hope the currency bloc will return to growth this year. ...