Montreal-based MTY Food Group, the franchisor of brands including Cold Stone Creamery, Baja Fresh, Pinkberry and many others, announced it is merging with Papa Murphy’s Holdings, the Vancouver, Wash.-based take-and-bake pizza chain. MTY control nearly 6,000 stores in 39 countries. Papa Murphy’s is the fifth largest U.S.-based pizza chain, with system sales of more than…