In what seems like an annual ritual, The Beatles have invaded pop-culture conversations, thanks to a new George Harrison documentary, a John Lennon biography and Paul McCartney’s collaboration with New York City Ballet. In the first of a three-part series, we start with a review of “Ocean’s Kingdom,” McCartney’s first ballet score. We’re joined by Jennifer Homans, dance critic for The New Republic and author of the ballet history “Apollo’s Angels.”