[TIMOB-19065] Windows: AlertDialog.show() fails when buttonNames.length >= 3

Ti.UI.AlertDialog.show fails when buttonNames have over three buttons on Windows Phone. It looks like it's a limitation of Windows::UI::Popups::MessageDialog on Windows Phone, so we might want to throw exception when over 3 names are assigned.

	Ti.UI.createAlertDialog({
		title: 'Title',
		message: 'Message',
		buttonNames: ['A','B','C']
	}).show();