Vivid Faces: The Revolutionary Generation in Ireland 1890–1923 by R.F. Foster Penguin, 2015, 464 pages, $24.99   In Ireland, so often it seems as though the past occurred within living memory. I remember as a postgraduate student in Dublin in the 1990s witnessing the moving commemoration of the Great Famine, an event that had occurred a century and half beforehand, but whose legacy was real and widely felt. The Irish past is current once more as I write this with the occurrence this year of the 150th anniversary of the birth of W.B. Yeats and the looming centenary in 2016…