A German billionaire who was heir to a coffee empire and one of the largest individual landowners in Newton County died after a boat struck him while he was swimming in Lake Rabun Saturday. Joachim Herz, 65, owner of the Little Springs Farm on Ga. Highway 36 in Newton County, was visiting friends at a lake house and swam out into the main channel away from the main swimming area when an 18-foot ski boat made a left turn and struck him, said Jennifer Barnes, senior public relations and information specialist with the Georgia Department of Natural Resources. The boater, a 43-year-old man from