Rebecca Rubin Senior Film and Media Reporter Avatar — the master of elements and not the blue alien creatures created by James Cameron — graced the main stage at CinemaCon, the annual convention of movie theater owners. Paramount didn’t preview any footage of the film based on the popular “Avatar” television series, though the studio unveiled the official title: “The Legend of Aang: The Last Airbender.” Previously titled “Aang: The Last Airbender,” the film takes place in a world divided into four nations — Water Tribe, Earth Kingdom, Fire Nation and Air Nomads.