Migdalia Cruz's "Fur" (presented by Boundless Theatre Company at Next Door @NYTW) has the sensibility of a folk tale, the coherency of a fever dream, and the trappings of a horror movie. It's an unsettling piece of theater. After you've seen it, don't be surprised if it noses its way into your psyche and burrows into your personal dreamscape. This production, directed by Elena Araoz, is the play's New York City premi…