- Add "isOlderThan" method to the "SanitizationService" to distinguish
old ToggleButtons with the property "option" from new ones
- Use SanitizationService.isUnitDefinitionOutdated in Player to set
the unitDefinitionVersion (should be modified!)

Fix import order

This button helps the user to detect if a page has additional,
hidden content

- Use done event of keyboard animation to set the scroll position
of the element
- In small browser views elements are scrolled to the top of the view
instead of the middle of the view

- Fix related tests

- 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'

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

This way elements can handle their logic themselves without having to
rely on outside utility classes.

Also restructure files in common in a more logical way.