YOU WOULD think that the authorities would have learned a lesson. They have made a wilderness. socially and economically of central Dublin. Few live there; few walk around it at night. Security men, dogs and the occasional wino have taken cover. The middle classes have uprooted and gone long ago. The poorer classes are left isolated in their high tenements institutionalised poverty, it is - from Donore Flats, through Fatima, across Cook Street by the barren wastes of Sean MacDermott Street to Summerhill, ending in the world's end of Railway Street and Sheriff Street.