The housing market is tight all around New England these days, but among the selling points for most homes, rarely is “haunted by a witch” high on the list. That’s a big part of the terrifying charm of the house on Round Top Road in Harrisville, Rhode Island — that, and the fact that the house was part of the inspiration behind the horror movie franchise “The Conjuring,” the eight movies from which have grossed more than $2 billion. And that’s precisely why Cory and Jennifer Heinzen, longtime residents of the Maine town of Mexico and paranormal investigators, bought it...