pixbufmanipulator: refactor to simplify and ditch the class

src/accountmigrationview.cpp

src/avatarmanipulation.cpp

src/chatview.cpp

src/client.cpp

src/conversationsview.cpp

src/currentcallview.cpp

src/incomingcallview.cpp

src/mainwindow.cpp

src/native/pixbufmanipulator.cpp

src/native/pixbufmanipulator.h

src/notifier.cpp

src/profileview.cpp

src/webkitchatcontainer.cpp