Only one of the dozen or so characters in “Boogie Woogie,” Duncan Ward’s beyond-nasty art-world satire, has the semblance of a soul. He is Dewey (Alan Cumming), a gay London gadabout and the best friend and promoter of Elaine (Jaime Winstone), an artistic exhibitionist whose would-be chef-d’oeuvre is a video diary of her ravenous sex life. That diary focuses on her lesbian encounters with women she stalks and surreptitiously records during their steamy couplings. Some might call it pornography.