Bill’s real world nous and sci-fi savvy is proving to be a real asset to the current season of Doctor Who. After last week’s detour into whimsical fairy tale storytelling, “Thin ice” brings us solidly back to a more grounded Who, and adds a dash of realism that has often been lacking in the series’ fifty-four year history. Having landed in 1814 London during the last frost fair, the Doctor and…