Something of an anomaly in the age of multi-screen households and fragmented viewing, the genuine all-ages family movie gets a canny but uncynical revival in “ The Sheep Detectives .” As bracingly odd a proposition to hit the multiplex as any we’ve seen in the last couple of years, the first live-action feature from long-serving Illumination director Kyle Balda (“Despicable Me 3,” “Minions: The Rise of Gru”) is a shaggy hybrid of creature feature and murder mystery that — minus the zippy anthropomorphic world-building of the “Zootopia” films — derives much of its charm and wit from the frank incompatibility of those genres. Here, sheep can’t solve crimes until human incompetence forces them to step into the breach; though pushed for the purposes of fantasy, the limits of animal intelligence are a poignant factor in the tale.…