Rename KeyboardComponent to KeypadComponent
Rename KeyboardService to KeypadService
Split LayoutComponent into LayoutPlayerComponent and
LayoutPagesComponent
Prepare the introduction of an additional keyboard

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.

- This improves scroll snap behaviour
- Set background color of page
- Interpret the margin of a page as padding. What it really is

Add styles for fixed right position
Customize markup for different positioning
Refactor Usage of KeyboardService in components

* Use IntersectionDetector for intersectionDetection directive
* remove unnecessary input 'index' from page component

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

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

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

* `UnitState.dataparts` has property `elementCodes` property, which
stores status, value and id for FormElement
* When building a unit, the stored value is assigned to the element
when it is initiated
* Removed `UnitState.dataparts.pages`
* Removed methods initPages and addStoredValues

* Bugfix for units without always visible page
* Bugfix for aspect ratio over 50%
* Integration of keyboard

Because the always visible page is now positioned at the first place of
the unit definition.

When this is set the page will only be rendered to that width. Otherwise 
100% of the available space is used.

In the past, the page index could be set by button click and after
scrolling, which led to unwanted side effects

To center the content of the player, the dimensions of all pages are
calculated.

* Move two different intersection detections from
`scroll-index.directive` and `section.component` to
`intersection-detection.directive`

* Fix bug for small pages
* Add functionality for tabbed pages
* Use layoutContainer as container for intersection detection
* Rename properties and methods

* Use `IntersectionObserver` to detect page position while scrolling

* Pages can be scrolled or tabbed
* Labels of pages can be shown and hidden
* Always visible pages can be left, right, top or bottom
* Layout of pages is now handled in `LayoutComponent` and removed from
`PlayerStateComponent`
* Due to the `ScrollIndexDirective`, pages with scrollbars have similar
interfaces as pages with tabs