I am developing Windows phone 8 PhoneGap app. Using navigator.app.exitApp() I am quiting the app from home screen in Windows phone 7. But when I tried the same in Windows phone 8, I am getting the error `Unable to get property 'exitApp' of undefined or null reference`. I would like to know why it is undefined in Windows phone 8 and not in Window phone 7 PhoneGap app. Also, I would like to know, is there any way to quit the app programmatically in Windows phone 8 PhoneGap app?.