As the RSC's artistic director steps down after an illustrious and radical 35 years and 50 shows, he talks about the productions he's most proud of, his new memoir, and the loss of his husband, the actor Antony Sher If Gregory Doran " Greg to his friends " were a character from Shakespeare, he would be best cast as Kent from King Lear because he has the steadiness, kindness and faithfulness of a self-appointed servan…