Three stars. Rated R. 100 minutes. Almost exactly one year ago, “I, Daniel Blake” won the Palme d’Or at Cannes, but it is only now fetching up on our shores. A slice of British working-class life from social-realist director Ken Loach and his longtime screenwriter Paul Laverty, this affecting portrait of an unemployed craftsman desperately trying to return to a life of dignity and productivity gives the lie to the myth that there are no films celebrating and reflecting white working-class culture.