The unbridled life and kaleidoscopic filmography of Piero Vivarelli, who made Italian B-movies of all genres, wrote hit rock songs and penned the screenplay for Sergio Corbucci’s Western “Django,” adored by Quentin Tarantino, are intertwined in a portrait of an unsung postwar provocateur and revolutionary (the only non-Cuban besides Che Guevara to be given a Cuban Communist Party card signed by Fidel Castro). The creative doc is also a prism into an unexplored territory of Italian — and by extension global — pop culture and its unique vitality.