Since Downton Abbey concluded, many of the actresses on that period series have gone defiantly against type, embodying roles that are more modern, or less proper, or both. Tonight’s fact-based period drama, Dark Angel, definitely does the latter, but goes back even further in time than the former. Set in the 1860s and 1870s, just after the American Civil War, Dark Angel stars Joanne Froggatt – who played sweet, long-suffering Anna Bates in the downstairs part of Downton Abbey –