One year after Superman, James Gunn’s DC Universe is up, up, and away. Returning to theaters with a movie about Big Blue’s 23-year-old cousin Kara Zor-El (Milly Alcock), Supergirl shows off the DCU’s intergalactic side. When we last saw Kara, she was picking up Krypto from Clark’s after a weekend of heavy drinking on some Red Sun planets, where her tolerance for alcohol isn’t so strong. But in Supergirl, she joins Ruthye (Eve Ridley) on a quest …