[TIMOB-18095] CLI: Finish implementation of Windows Phone Package hook for Windows platform

I'm not sure how exactly we sign WP 8.1 apps. We can do XapSignTool as commented out here: https://github.com/appcelerator/titanium_mobile_windows/blob/master/cli/hooks/wp-package.js#L29 But I think that's for "company apps" which I guess is sort of like adhoc distribution for iOS? http://msdn.microsoft.com/en-us/library/windows/apps/jj206724(v=vs.105).aspx