GLOBAL MARKETS-Euro, sterling buoyant before central bank meetings

* ECB and BoE in focus; euro and sterling near recent peaks* Shares, bonds make ground as Yellen bolsters supportive Fed view* Putin urges separatists to postpone Ukraine secession vote* China exports, imports beat forecastBy Marc JonesLONDON, May 8 (Reuters) - Expectations the European Central Bank will keep its policy powder dry for another month at least kept the euro near a two-month high on T