The 1975 cinema vérité classic Grey Gardens, which captured in remarkable close-up the lives of the eccentric recluses and cousins to Jackie Onassis, Big and Little Edie Beale, in their decrepit East Hampton mansion, has spawned everything from a midnight-movie cult following to a Broadway musical remake an upcoming Hollywood adaptation. Now, Albert and David Maysles have revisited their landmark documentary with a sequel of sorts, culled from hours of never-before-seen footage recently found in the filmmakers’ vaults.