WATERTOWN — To UPS customers, Nathan Burk is remembered for his beaming smile when he delivered packages. And for the dogs, it’s the treats he made sure to keep in his pocket. When he stopped at Torrington Regional Animal Control Facility, he’d make sure he’d bring a treat for each dog in its care, staff recalled. Burk, 28, of Waterbury, a five-year employee for UPS, died Tuesday night following an assault in a UPS truck on Route 8 north. Elijah D. Bertrand, 19, whose last known address was in Coventry, was charged with murder and will be arraigned this morning in Waterbury Superior C...