Even those who consider themselves experts on the subject will find a provocative treasure trove of images and anecdotes in “Skin: A History of Nudity in the Movies.” Danny Wolf’s documentary is a breezy, open-eyed, and often encyclopedic compendium of all the ways the cinema has celebrated, exploited, and negotiated the power of the naked body. The film kicks off with a montage of actors and directors — Sean Young, Eric Roberts, Peter Bogdanovich — recalling the first movie they ever saw that had nudity in it, and that allows the film, in its early moments, to leap through some of Nudity’s Greatest Hits (“Ecstasy,” “Last Tango in Paris,” “The Blue Lagoon,” “Fast Times at Ridgemont High”).