With echoes of Catherine Breillat, Lucille Hadzhihalillovic, and Peter Strickland, “Piaffe” rides a deep tail of sexual awakening. The feature directorial debut of Berlin-based visual artist Ann Oren, “Piaffe” follows Eva (Simone Bucio), an introverted and unqualified woman who grows a horse’s tail while foleying sound for a commercial about an equine-inspired drug.