replaced every possible std::string with QString

src/gui/official/Account.cpp

src/gui/official/Account.hpp

src/gui/official/Call.cpp

src/gui/official/Call.hpp

src/gui/official/CallStatus.cpp

src/gui/official/CallStatus.hpp

src/gui/official/Event.cpp

src/gui/official/Event.hpp

src/gui/official/EventFactory.hpp

src/gui/official/EventFactory.inl

src/gui/official/ObjectFactory.hpp

src/gui/official/ObjectFactory.inl

src/gui/official/ObjectPool.hpp

src/gui/official/PhoneLine.cpp

src/gui/official/PhoneLine.hpp

src/gui/official/PhoneLineManagerImpl.cpp

src/gui/official/PhoneLineManagerImpl.hpp

src/gui/official/Request.cpp

src/gui/official/Request.hpp

src/gui/official/RequesterImpl.cpp