A planet of executioners! A call from the Vatican! A surprise visit from Missy! Nardole’s bad-ass moment! Bill’s ruined date! There’s a whole lot to talk about in “Extremis”, Stephen Moffat’s latest (and last?) attempt to write a story that deviates from the “Doctor Who” norm. We liked it a lot, but that won’t stop us from nitpicking about how random number generators work…