Newfoundland and Labrador has reached a tentative deal with Quebec over power flowing from the Churchill Falls hydroelectric plant that could reap hundreds of billions of dollars over the next five decades.Newfoundland and Labrador Premier Andrew Furey and Quebec Premier François Legault are announcing the terms of a memorandum of understanding at a news conference in St. John’s this afternoon.In a sweeping agreement that not only replaces a contentious 65-year contract that generations of N.L. politicians have loathed, Furey and Legault also announced plans to develop Gull Island, one of the last great hydroelectric projects in North America. “​Today, everything changes for Newfoundland and…