Remove shared groupbox_qt header for wxQtGroupBox stub (real wxQT internal hepers will be implemented for wxStaticBox and wxRadioGroup)
Implement wxQtGroupBox and wxQtRadioBox internal helpers (just to handle qt events as no signal connected by now)
Add wxQtButtonGroup internal intermediate helper to connect wxQtRadioBox (QGroupBox) button signal. Note this one is not a 'visual' control so it doesn't derives from QWidget, then using wxQtSignalHandler instead of wxQtEventSignalHandler