Death is a given, but not the time-honored rituals. An increasingly secular, nomadic and casual America is shredding the rules about how to commemorate death, and it’s not just among the wealthy and famous. Somber, embalmed-body funerals, with their $9,000 industry average price tag, are, for many families, a relic. Instead, end-of-life ceremonies are being personalized: golf-course cocktail send-offs, backyard potluck memorials, more Sinatra and Clapton, less “Ave Maria,” more Hawaiian shirts, fewer dark suits. Families want to put the “fun” in funerals. . . .