* Add IntersectionService
* Add CompoundElementComponent as parent for LikertComponent
* Inject ElementRef to common ElementComponent
* Rename players' ElementComponent to ElementContainerComponent

* Remove FormService Injection
* Move FormService and form types to player
* Move interface ValueChangeElement to uI-element.ts
* Use interface InputElementValue instead of
string | number | boolean | null

* Add `InputElementValue` as type when needed

Should at least be in util folder. And since it is imilar functionality 
to the unit factory it is placed within.

* Background: white
* Fontsize: x-large

Make sure that selection start is smaller than selection end

* Remove general (full) keyboard in layout component
* Implement French keyboard component

to avoid name collision.

Use static readonly property MARKING_TAG to define tag name of marked
text

This is rather hard to implement via HTML inline style attributes. So we 
do it the classic way.
Could be reviewed, when that feature is implemented in TipTap:
https://github.com/ueberdosis/tiptap/issues/1514.

* When elements receive the focusin event, their status is changed to
`TOUCHED`
* Replace `this.form.valueChanges` subscription with
`this.unitStateService.unitStateElementCodeChanged` subscription

* Take over tasks of `UnitStateComponent`
* Manage property `unitStateElementCode`
* Removing the passing of the property `unitStateElementCode` by
the components

Console logging is disabled in production mode by overriding the
function in `main.ts`

* Implement as draggable overlay
* Keyboard can be configured as 'mini' or 'full'