SPRINGFIELD — Nathaniel Onsrud was released from prison this week after the Rock Island State’s Attorney’s Office agreed to vacate his 2008 murder conviction, in light of new documents that surfaced with help from the Illinois Innocence Project.Rock Island County State’s Attorney Dora A. Villarreal also announced her office will be auditing all cases handled by Margaret A. Osborn, the former assistant state’s attorney who obtained Onsrud’s guilty plea.The order to vacate Onsrud’s …