The given serialized properties may not conform to all UIElement 
properties. They are merely meant as a building plan; they may also 
contain outdated properties which have to be transformed when reading.

Basically a div with border properties as usual.

Create object list, when none is existent yet. Otherwise append as 
before.

Now correctly reads the value IDs of drop list elements, so they can not 
be used again.

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.