Handling of keyboard events : Key Down.
\param key : unicode code of key
\param keyCode : virtual keycode for non ascii keys - see \ref VirtualKeyCodes in keycodes.h
\param modifiers : any combination of modifiers - see \ref KeyModifier in keycodes.h
\return kResultTrue if the key is handled, otherwise kResultFalse. \n
<b> Please note that kResultTrue must only be returned if the key has really been
handled. </b> Otherwise key command handling of the host might be blocked!
Handling of keyboard events : Key Down. \param key : unicode code of key \param keyCode : virtual keycode for non ascii keys - see \ref VirtualKeyCodes in keycodes.h \param modifiers : any combination of modifiers - see \ref KeyModifier in keycodes.h \return kResultTrue if the key is handled, otherwise kResultFalse. \n <b> Please note that kResultTrue must only be returned if the key has really been handled. </b> Otherwise key command handling of the host might be blocked!