DOCUMENTARY MINISERIES PREMIERE: BBC America’s weekly Saturday night unveilings of original Saturday night nature documentary series continues with this latest one, a multi-part visit to Yellowstone. In this opener, the filmmakers look at the national park in winter. That’s when I visited the park, back when they allowed people to rent snowmobiles and roam freely. My old faithful friend John Sawinski planned the multi-family ski trip then, and rented our vehicles. What a guy. And, along the way, what a geyser…