EntertainmentFor the past three seasons of Showtime’s The Big C, Laura Linney’s cancer-stricken character, Cathy Jamison, has gone through three stages of grief – denial, anger, bargaining.  In the season that launches April 29, subtitled “Hereafter,” Cathy will reach the stage of acceptance.  This is a different kind of a season – with four two-hour episodes they’re calling a “limited series event.” Fans of the under-appreciated series will not be surprised that despite these ominous signs, there is a lot …