NEW YORK (Reuters) - Democratic front-runner Hillary Clinton promised on Saturday to fight for ordinary Americans who have been left behind as the economy recovers, appealing to working families at the first major rally of her 2016 White House campaign. Speaking on New York's Roosevelt Island, within sight of Manhattan's skyscrapers, Clinton promised would "make the economy work for everyday Americans, not just those at the top" if elected president. The gathering of several thousand people cheered as Clinton said working people are asking why wealth is reserved for chief executives and hedge fund managers. "You have to wonder, when...