[TIMOB-19063] Windows: default background color of sample apps

On Windows Phone, background color of components tend to be transparent, and the text color tend to be set white.This causes confusion when Window color is white, because some components like Label and Button looks disappear. The issue is that some sample apps from Appcelerator tend to have white background color by default, which might be looking good with iOS. But on Windows Phone we need to make it black or something other than white. So make sure sample app does not have white background:

var isWindows = (Ti.Platform.osname === "windowsphone" || Ti.Platform.osname === "windowsstore");
var window = Ti.UI.createWindow({
	title: 'Todo',
	backgroundColor: isWindows ? '#000' : '#fff',
	navBarHidden: false,
});