PITTSBURGH — After nearly two months of waiting, Astros top prospect Jonathan Singleton has a target destination. Astros general manager Jeff Luhnow said Sunday that Singleton will likely make his 2013 debut next week at low A Quad Cities, then move up to Class AAA Oklahoma City. “He’s been playing. But it’s different playing under the lights at extended (spring training),” Luhnow said. There’s a chance Singleton could spend time at Class AA Corpus Christi before moving to OKC. A final decision won’t be made until the Astros’ evaluate Singleton’s initial performance and their minor league teams’ upcoming schedules. “For sure Quad Cities and he’s ultimately going to end up [...]