'Downton Abbey's' final season seems intent on sticking the landing

All along, "Downton Abbey" has busily issued fond goodbyes to the way things used to be a century or more ago; to the very end, it's a show about the difficult transition and eventual extinction of a particular strain of the upper class, luxuriating in a lifestyle that Anglophilic viewers and fans of the show hold dear. Now, in its sixth and final season, which begins Sunday night on PBS's "Masterpiece," the hardest truths of the 20th century are no longer abstract or optimistically shrugged asi...