By Bob Weber THE CANADIAN PRESS EDMONTON- They’re affixed to old buildings where someone important used to live. Or they’re mounted on a rock overlooking somewhere where something once happened. Cast in bronze or lettered on a sign, they’re sometimes the only history lesson many of us ever get. And now Parks Canada wants hundreds of them changed. “The way that many of the national historic designations are framed and positioned does not do justice to the breadth of impacts that they had on Canadian society,” said Pat Kell, the agency’s director of heritage. Parks is in the middle of a three-year program to re-examine and rewrite the plaques that the Historic Sites and Monuments Board use to point out places deemed important to understanding Canada’s past. Sites slated for…