The indictment reads like a cinematic plot: A Harvard Fellow and another activist allegedly wanted to buy AK-47s, Stinger missiles and grenades to topple South Sudan’s government. What they lacked was enough cash.Now, Jane Street co-founder Robert Granieri concedes he put up the money — saying he was duped into funding the alleged coup plot. The admission from the wealthy recluse behind a Wall Street trading powerhouse stems from the US prosecution of Peter Ajak, the Harvard Fellow who was accus...