It’s been thirty years since the fall of the Berlin Wall and the end of the divide between East and West Germany. The anniversary was marked this week at Symphony Hall, where a German orchestra conducted by the Boston Symphony Orchestra’s Andris Nelsons performed two shows commemorating the “Peaceful Revolution” leading up to that event. The shows were part of the second “Leipzig Week” in Boston, named after the town in Germany that houses the acclaimed 275-year-old Leipzig Gewandhaus Orchestra. The two orchestras kicked off a partnership last year, which includes musician exchanges, shared performances, and the touring of both orchestras in their respective home countries – all under the guidance of Andris Nelsons, the music director for both groups. Jim Braude was joined by Andris Nelsons, music director of the BSO and of the Leipzig Gewandhaus Orchestra.