It’s already becoming a bit of cliché to say that a film (or book, or show, or album) is Actually About Grief and Trauma, and I’d imagine this will only get worse in the months and even years to come. But Stacey Gregg’s dramatic thriller “Here Before,” which is about a woman who comes to believe that the new neighbors’ daughter is the reincarnation of her own lost young one, is actually about grief and trauma, and handles those topics with delicacy and grace. And then it’s shocking and creepy, on top of that.