Ukraine leader urges unity to bring change, combat Russian 'aggressor'

By Natalia Zinets and Richard Balmforth KIEV (Reuters) - Ukrainian President Petro Poroshenko called on all political forces in the country on Sunday to rally behind his plans for constitutional change aimed at ending a separatist conflict in the east and defeating what he termed the "Russian aggressor". Poroshenko used a flag-raising ceremony in Kiev on the eve of Independence Day to make a clear pitch to his coalition allies to overcome their doubts and vote in favour of amendments to the cons