After a unit definition is read, the deprecated properties are deleted.

This controls the general font size. Specific spans can still be styled 
individually in the text editor.
- The TextEditor also uses this font size as default when rendering the 
text.

see Verona Api

- Now correctly exchanges the simple ui element objects with constructed 
objects.
- Also remove the unnecessary variable childElements. The child elements 
can be gotten from the parts. As it is done in the component method 
getFormElementModelChildren.

Now correctly used the value of the dropped element.

- Remove function call in template
- Init value with elementModel.value
- Set readonly and disabled properties in template and remove OnInit
- Compact code

Use a copy of the original elements to avoid accidentally changing them.

The version used does not support the new json-ld format yet and errors
out.

# Conflicts:
#	projects/common/models/uI-element.ts
#	projects/editor/src/app/app.module.ts
#	projects/editor/src/app/components/unit-view/page-view/properties-panel/element-model-properties-component.component.ts
#	projects/editor/src/app/services/dialog.service.ts

This is ised to flatten objects for the proerties panel.

The change of moving some properties to sub objects broke the creation 
of the combinedProperties object, which can't deal with nested objects. 
To circumvent that all elements are now flattened before being combined.
The connected property panels now again look for the properties on the 
element itself and not in sub-objects.

If the property is set, the video will be scaled as far as its
container (static element or grid) allows, otherwise only up to its
maximum native size.

If the property is set, the image will be scaled as far as its
container (static element or grid) allows, otherwise only up to its
maximum native size.

When the magnifier was moved to the right of an image, there was a
possibility that a scroll bar would flare up, depending on the size
of the image. By subtracting the frame width of the magnifier the error
is fixed.

- Dnd values now have a special type that has an ID, a string and
  another string for an image path.
- A new dialog exists for editing thoe options. Similarly to the likert
  header.