Elvis Costello has built an illustrious career around not being a conformist. He has dipped his fingers into so many musical genres and collaborated with such a wide range of music legends that it is hard to know which Elvis will show up during his annual summer stop at Wolf Trap. Will it be angry, loud, rocker Elvis (2002)? Romantic Elvis (2004)? Country and bluegrass-infused Elvis (2005)? It is precisely that uncertainty that makes the…