CBS is the network of crime. The CSI franchise, “Cold Case,” “Without A Trace.” So “Dexter” should feel right at home. The superlative Showtime series about a Miami forensics expert (Michael C. Hall) who moonlights as a criminal killer debuts on mainstream TV on Sunday. CBS boldly scheduled “Dexter” to fill the void left by the writers’ strike, and, amazingly, it didn’t require much editing. Bob Greenblatt, Showtime’s president of entertainment who did the editing on the 12 episodes of Season 1, said most of the cuts were for time constraints and language. “Dexter” is disturbing TV but most crime viewers who have never seen it will love it. “Dexter” deserves a mass audience and the Emmy exposure.