(By Joe Kukura) Life becomes worth living again, as NFL teams have opened their training camps league-wide. We contemplated the nascent Oakland Raiders Tuesday, and the consider the similarly-underdog 49ers today. The two teams will play to open their preseason Friday at 7 p.m. at McAfee Coliseum. Leadership voids -- who's gonna fill 'em? Leadership voids are the only thing these 49ers know for sure they have. Sure, Patrick Willis has a fucking "S"......