Polar bears are growing increasingly comfortable around people, and that’s a problem. One can see the tension between these natural hunters and those who hunt them — whether that happens with telephoto lenses or high-powered rifles — in Churchill, Manitoba, self-proclaimed “polar bear capital of the world,” where tourists flock when the magnificent animals migrate in order to catch a glimpse of the threatened (but still quite lethal) species. In their Sundance-winning feature doc “ Nuisance