Similar to a text element but parses the text on change an replaces 
markers with actual elements.
The text is then displayed inline with the elements.

To make it's purpose clearer.

- Remove interfaces
- Add classes for all elements as well as unit, page and section
- 2 intermediate interfaces are kept. They dont constituate a viable 
object but only additional properties, like background-color. Those can 
be added as interface to all elements. Initialisation has to be done by 
the element itself though and not by some constructor higher up.