Jem Cohen’s “Museum Hours” is a contemplative, leisurely look at the world of art as a parallel to ours. A loose narrative pulls together the director’s musings on the correspondence between the two. The story, such as it is, introduces us to a Canadian woman (singer Mary Margaret O'Hara) who travels to Vienna to visit a cousin she hasn’t seen in years and who has fallen in a deep coma with little chance of recovery. For someone