“Howl,” a movie about werewolves on a train, is decent but ultimately lacks substance or any real moral compass. The story centers around passengers aboard an English train that must band together to survive after it’s unexpectedly halted in a dangerous forest—a forest inhabited by werewolves. This 2015 British film draws inspiration from several sources: the werewolf elements of “Howling VI: The Freaks” (1991…