Thomas Wolfe may have felt strongly about never being able to go home again, but to filmmakers and Hollywood executives there is creative and box office salvation in returning to the beginnings of a popular movie franchise. In the neverending quest to sell tickets, the movie “prequel” (a word that somehow never sounds right) is becoming a box office force — a trend that seems to please popcorn junkies and showbiz suits looking for a safe bet. Just ask 007, who simultaneously returns to theaters and introduces himself this week in “Casino Royale.”