Feature Request: Styling Options for Headings and other predfinied CSS classes

```
It would be nice to have a graphical GUI to style headings and other predefined 
CSS ( or create new classes), so that the user who doesn't have knowledge about 
html5 can easily change the attributes of the classes and by that suit the 
document for his/her needs.
```

Original issue reported on code.google.com by `s.eickm...@student.rug.nl` on 10 Jun 2015 at 12:46
