(plaintiffs were injured in collision with farm tractor and disc mower; neither tractor nor mower were insured; plaintiffs sought coverage under uninsured provision in their policy, which was denied; plaintiffs brought breach of contract claim against defendant; defendant granted summary judgment because farm tractor not “motor vehicle” as defined by insurance policy and plaintiffs appealed; appellate court affirmed because tractor not designed to operate primarily on highways and not required to be registered, tractor is not a motor vehicle under state No-Fault statute or under policy as a matter of law; reasonable expectations doctrine is also not applicable because definition of motor vehicle in policy is not ambiguous).