When calling the element constructor may generate IDs. Those appear as 
already registed later when the unit is instantiated for real.

- Do ID checks only in the class, not in unit service (or elsewhere)
- Fix repaired value list to get new objects instead of references to 
the existing.

There should never be the case, therefore error out.

- Use Unit's getAllElements method of Unit instead of
UnitUtils.findUIElements to get all DragNDropValueObjects
in UnitComponent
-Remove unnecessary timeout in UnitComponent

- Sanitize without using unit definition version

- This makes the behavior identical to real form elements
- To trigger the focusout event, the HTML element needs
the tabindex attribute

simple dropdown lists need a minimum height so they don't collapse
if they don't contain any element

Using disabled cause conflicts with reactive form in player

- Add "isOlderThan" method to the "SanitizationService" to distinguish
old ToggleButtons with the property "option" from new ones
- Use SanitizationService.isUnitDefinitionOutdated in Player to set
the unitDefinitionVersion (should be modified!)

The equality check compares the reference of the array and not the
values of the array.

Use css grid instead of flex plus calculating margins in template

Using the html property "disabled" results in a warning message in the
player when reactive forms are used at the same time.

Use the same settings as in simple drop list

ViewEncapsulation.None is required for overriding tooltip

DragNDropValueObject no longer has the stringValue property
but a TextLabel with text

Aslo create new props panel component and move border stylings to 
separate fieldset (wihtin the styling tab).

#291

One as a general label above the table and one for the first column 
heading.

Since this is no proper InputElement separate properties panel inputs 
are used.

#272

To be the same as with Material inputs.

#319

Add new parameter 'itemsPerRow'. This limits the grid columns used, 
making items move to the next row if overextending.

Also simplify component structure.

Move label creation to ElementFactory.

No way has been found to have an abstract static method for 
OptionElement's label generation, therefore silence the linter.
Same for getElementComponent.