This removes all the classes and goes back to simple interfaces for
unit, pages etc and all elements. This makes creating them easier and
cleaner.
Things like specific needs when setting element properties and most
importantly compatibility handling is done by a special service module,
that knows all the elements and how to repair old their potentially
outdated definitions.

This is done according to the Angular best practices and minimizes
namespace collisions when using other packages which might use the same
selectors.

Technically the selectors are not even becessary since we use an Angular
component factory to create element components but it is still useful
for the DOM element naming, for debugging purposes for example.

- Remove element as parameter

- Implement marking buttons as toggle buttons

This disables the possibility of nested markers

The marking service takes over the conversion to rgb notation, because
in html markup this notation is used for the background color