Splash screen during app launch / custom background color for window

```
An option in settings.json to set an image for a splash screen. This is to 
prevent user seeing a blank window with white background during application 
launch while loading start page. CEF callbacks OnLoadingState/OnLoadEnd should 
be used to determine when web page loading has completed.
```

Original issue reported on code.google.com by `czarek.t...@gmail.com` on 20 Nov 2014 at 6:06
