All MainWindow child widgets use constructors with 'parent' parameter
that allows parent widget to delete them at its destruction.
Some other MainWindow cleanup code replaced to destructor.
Application manages MainWindow instance and remove it when aboutToQuit()
signal emitted.
Change project directory structure according to application structure.
Change 'nox' configuration option to something more meaningful 'nogui'.
Rename 'Icons' folder to 'icons' (similar to other folders).
Partially add 'nowebui' option support.
Remove QConf project file.
