It’s like old times for “Law and Order.” The NBC crime drama is back in its old Wednesday night stomping grounds, relevant and reinvigorated, and winning the night for its network. NBC was wise not to cancel the old workhorse and got lucky when the writers’ strike made viewers desperate for anything new. The familiar format still works in the crime drama’s 18th season while new cast members Jeremy Sisto (Cyrus Lupo) and Linus Roache (Michael Cutter) have given the show a much-needed spark. Sam Waterson (Jack McCoy), who has moved into the District Attorney’s office, remains “Law and Order’s” heart and soul. “Gunsmoke’s” record run of 20 seasons is in big danger. P.S., “Law and Order” may soon have a British TV edition, “Law and Order: London.”