SEASON PREMIERE: One of the few new bright spots on broadcast TV last season, Once Upon a Time took its fairy-tale premise, and its Disney imprimatur, and emerged with the best mythic mystery series since Lost. That enchanting season ended with a cliffhanger, as all the residents of Storybrooke were freed from their amnesiac spells, and Mr. Gold – a.k.a. Rumpelstiltskin – enveloped the town with a mysterious purple mist. What will the mist do? Tonight’s Season 2 opener, obvious