Elizabeth Diller, designer of the Boston Institute of Contemporary Art on the city’s waterfront, will give a lecture at 3pm Saturday at the Boston Public Library in Copley Square. The talk, which is free and open to the public, is part of the annual “Druker Lecture Celebrating Design and Architecture.” The lecture series is the result of an endowment established by Boston developer Ronald Druker, president of The Druker Co., which explores an understanding and appreciation of urban design…