Work on QtConsole Menu * add new_frontend_factory, slave_frontend_factory callable arguments to MainWindow constructor, decoupling MainWindow and the IPythonApp a bit * create *all* menu items in MainWindow.init_menubar, rather than some in the IPythonApp * split init_menu_bar into methods for each menu, to ease organization * attach all menu bar actions to the MainWindow as well, so that they are still accessible when Menu Bar is invisible * add View menu for Fullscreen and Fonts * organized menu items to match standard patterns * Fewer platform-dependent menu items