Authentic, creative and packed with cross-clenching tension, Daniel Stamm’s “The Last Exorcism” almost had it all, but instead suffers from a dreadful storyline. However, authentic performances, creepy settings and shaky camera angles keep Stamm’s film from completely drowning. Louis Sweetzer (Louis Herthum) believes his 16-year-old daughter Nell (Ashley Bell) is possessed by demons. Agnostic “Reverend”…