SEASON OPENER: It’s the start of the final season of Boardwalk Empire, and the show’s writers and producers are using the opportunity to go backward as well as forward. Tonight’s opener, for example, spends quite a few scenes going back to Nucky’s childhood, and showing his early efforts to get an advantage, get ahead, and ingratiate himself with the powerful and influential Commodore, despite being less athletic or charming than the other Atlantic City wharf rats. Meanwhile, in the “present” day of 1931, the adult Nucky (Steve Buscemi) is pulling the strings, and averting dangers, while on a work-related, and rum-related, visit to Havana. Patricia Arquette co-stars.