Provide default stylesSet sample with more features

[Alfonso Martínez de Lizarrondo]

There are some things that should be included in the default stylesSet sample so it's more useful to learn how to use it:

• Styles for the div container: #4973
• How to apply classes

The default stylesheet might need also some adjustments to reflect those classes.

[Jakub Ś]

I agree:

1. styles for divs
2. how to apply classes - information that all you have to do is apply class name but the class has to be either in contents.css or page styles(inline editor).
3. link to default file or code from default file.
4. link to config option explaining how to set your own styles - ​http://docs.ckeditor.com/#!/api/CKEDITOR.config-cfg-stylesSet