Dave Hickey, a prominent American art critic whose essays covered topics ranging from Siegfried & Roy to Norman Rockwell, has died.His books, including “The Invisible Dragon: Essays on Beauty” (1993) and “Air Guitar: Essays on Art & Democracy” (1997), won him legions of fans beyond the art world experts.His stylish prose, brash criticism of taste-making institutions like museums and universities and equal embrace of works considered both high- and low-brow left a lasting influence on a