- 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.

This is to convey a successful operation.

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.

- upgrade @ngx-translate/core
- upgrade rxjs
- upgrade testcafe

- run npm update

- Fix type of selectedGroup