Not quite a conventional horror movie, not pretty a coming-of-age drama, and not rather a accurate supernatural fable, Christopher Murray’s “Sorcery” is a tricky film to categorize. It’s dark, grim, and offended, like a revenge horror movie. There are moments of magic in a 19th-century environment that carry a form of fairy tale environment to head. And sure, this is a movie about a younger girl’s journey of self-discovery. But “Sorcery” is also inspired by true, unsettling historic details about how a beautiful, indigenous tradition was uprooted by European colonialism. All that to say, “Sorcery” is a movie with fairly a couple of themes, possibly way too quite a few,…