In ControlBarComponent the property project replaces the property
isAspectPlayer. It ensures that delays are used only in the player
and hints are always visible in the editor.

All elements now use the elementValueChanged event. Also
formValueChanged is changed.

AudioComponent and VideoComponent inherit from
MediaPlayerElementComponent to avoid duplicate code

* 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

- Remove interfaces
- Add classes for all elements as well as unit, page and section
- 2 intermediate interfaces are kept. They dont constituate a viable 
object but only additional properties, like background-color. Those can 
be added as interface to all elements. Initialisation has to be done by 
the element itself though and not by some constructor higher up.

The urls must be declared as trusted to be accepted by the application.

Also refactor a lot of stuff belonging to this:
- You can edit the default values via properties panel
- All elements now again have a common parent directive. form elements
have a special parent for forms.

* Only elements which has to be registered by the player's form inherit
from `FormElementComponent`
* Element components use their specific `elementModel`
* Rename file for `FormElementComponent`

The UIComponents now only have the properties they can make use of. This 
means that the angular components use the CSS properties explicitly 
instead of having all kinds of useless CSS properties.
Also it is no longer needed to update the CSS styles via event because 
Angular's change detection takes care of that.

This makes the actual component elements agnostic to any drag and drop 
and selection logic, which is handled completely via the 
wrapper-overlay. Now the component elements can be easily used by the 
player.

They will be reused by the player.