Iconoclastic Austrian indie director and former New German Cinema actor Peter Kern isn't just the subject of Veronika Franz and Severin Fiala's "Kern," but also the low-fi film's strongest creative force. He appeared in more than 70 feature films and directed a further 25. At his peak, Kern worked with the best directors of his era, including Rainer Werner Fassbinder (Fox and His Friends, The Stationmaster's Wife), Hans-Jurgen Syberberg (Hitler: A Film From Germany) and Wim Wenders (Wrong Move).…