A Chinese immigrant who stole trade secrets from the Chicago Merc worth an estimated $50 million was spared prison Tuesday by a federal judge who cited his otherwise “exemplary life.” Chunlai Yang, 50, of Libertyville, was instead sentenced to just four years probation for stealing software that underpinned the CME Group’s Globex trading platform. Yang, who worked as a high-ranking programmer for the Merc from 2000 until his arrest in 2011, pleaded guilty in 2012 to the theft, admitting he was trying to create a similar product in China when he illegally downloaded more than 10,000 computer source code files....