RECOMMENDED &amp;#8220;You&amp;#8217;re either part of the solution or part of the problem,&amp;#8221; Eldridge Cleaver is often quoted: as documentaries go, &amp;#8220;The Black Power Mixtape 1967-1975&amp;#8243; solves a few common production problems with its origins, drawing on a splendid cache of black-and-white and color 16mm interviews, shot in the United States by Swedish journalists with a [...]