BBC: "The next economic boom is going to happen in northern Canada and Churchill’s going to be a part of that." So says Mike Spence, a part Cree Indian and part Orcadian Scot who is mayor of the tiny Canadian settlement of Churchill on Hudson Bay. When I first arrived in the sub-Arctic town in early October, I found his claim hard to believe. No one was on the streets as I wandered alongside a freight train which had just arrived from Winnipeg, 1000km (600 miles) …