to ensure that a section that is not displayed has no dimensions

Call emitter in template and remove unnecessary method

Sections use the mediaStatusChanged event, which is also used to map the
interdependence of media elements

This can be enabled for TextFields and TextAreas and shows a keyboard
at the bottom of the screen. This does NOT set the field to read-only
which is probably wanted in a situation where the system keyboard is not
to be used. For flexibility purposes it is not implicitly set and needs
to be set manually. The same goes for other input assistance settings,
which should not be used in addition to the keyboard but it is allowed.

The keyboard has an extra switch to additionally show french special
characters.

Move KeyInputModule to the modules subfolder
Create template file for AppComponent

Rename properties and events for keypads

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

see commit #866a33c6

Replace custom pointer events with native pointer events

By default, text fields and areas only allow the input of keys from the
respective keyboard.

and in ElementFormGroupDirective

Reduce the number of input parameters in FloatingKeyboardComponent
Move double-used method to KeyboardService

Instead, use Textfied component with the property isClozeChild

Replace the direct method calls in media player components with events.
For this purpose, expand the inputs of the media player components that
are defined in the ElementMediaPlayerGroupComponent.

- Units and element are now built via the factory. This ensures only the
  wanted properties are present. All others are discarded.
- Since the sanatizer is supposed to check the unit defintion version
  it is used by player and editor and therefore put in common.
  This in turn makes it necessary to put the JSON resolver settings
  in the root-TSConfig file.
- Renamed a couple of properties to have clearer names.

- Verification is task of the common sanitizer
- Remove unnecessary AlertDialog

- Reimplement UnitStateComponent as central point to send the collected
information
- Implement ValidationService to determine the responseStatus of all
forms

This was necessary after the surrounding element container with its
styles and classes was deleted

Remove manipulations from elementModel
- Refactor drop list component
- Use of initial values for audio and video playback time

Defining the validators not in the elements anymore, but when creating
the forms