JERUSALEM — A Jewish group in Jerusalem is using 21st-century technology to map every tombstone in the ancient cemetery on the Mount of Olives, a sprawling, politically sensitive necropolis of 150,000 graves stretching back three millennia. The goal is to photograph every grave, map it digitally, record every name, and make the information available online. That is supposed to allow visitors to find their way in the cemetery, long a bewildering jumble of crumbling gravestones and rubble surrounded by Arab neighborhoods in east Jerusalem. Beset for many years by neglect, it is among the oldest cemeteries in continuous use in...