- Fix related tests

- Now only UIElements are found
- HTML parts of the text editor are ignored

- FloatingMarkingBarComponent no longer has the elementModel property

- Error was raised when loading a second unit. It was caused by the
binding of the UnitStateService to the UnitMenuComponent

- rename variables, methods and properties
- reduce attributes for methods
- split code in sun methods

- remove prefix 'on'
- split methods

- Remove prefix 'on'

- Remove prefix 'on'

- Rename methods with prefix 'on'

SectionVisibilityHandlingDirective now controls the visibility of
sections that depend on an audio or video

Elements read as classes were overwritten by the plain objects passed to 
the constructors.