His work has immersed him in events that read like a roster of recent catastrophes, from 9/11 to the Gulf oil spill. Now, Kenneth Feinberg is adding the Boston Marathon bombings to that list. The Massachusetts native and attorney is managing the payouts from The One Fund, which was established to help victims of the explosions that killed three and injured 260. Feinberg is experienced dealing with people facing profound loss, but he doesn’t seek the work.