For elements which don't have this functionality the workaround is to 
use pointer events and make the elements unclickable.

* Add IntersectionService
* Add CompoundElementComponent as parent for LikertComponent
* Inject ElementRef to common ElementComponent
* Rename players' ElementComponent to ElementContainerComponent

This improves bold text readability.
This has to be done in the actual element, in the TextEditor and on the 
properties panel.

Add 10px margin between label and options.

When the label is empty a smaller input field will be rendered which 
also does not have the label placeholder.

This has been refactored already. Those were not cleaned up properly.

Useful for longer text in textareas and does not hurt short text 
elements (like text-field).

This way the vertical size can be controlled.

Other elements do implement the interface but do nothing with the 
property. This make all the interface handling a lot easier at the cost 
of having useless variables in some contexts.

By clicking anywhere but elements of the side panels.

The outlines where not completely shown when multiple elements were put 
beside one another. Now the selected elements of pulled to the top and 
the outline is visible.

This is to not make them move (the amount of pixels the border has) when 
selected.

Some things had to be tweaked in regards to positioning and sizing of 
elements.
The drag preview is now done with a separate div, which only shows while 
dragging and has the temporary dimensions of the element. When dropped 
it sets the grid values if the dropzone as before.

* 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

* Add `InputElementValue` as type when needed

Since no default size is set, the default font size is set to 16px, 
which is the browser(?) default on my PC.

Margin between lines and between button and it's label.

Before it was done with a dysfunctional hack. Now with proper extensions 
to existing (tiptap-node-)extensions.
Also reads existing style and sets select-element accordingly.

Use proper types and remove unused vars.

No longer is async. For elements which need upfront source info (media), 
the media prompf is done in the unit service. Here we can keep it 
simple.
Also remove coordinates from factory as this is information that does 
not need to be known here. This is also handled in the unit service 
where applicable.

Remoove unnecessary type casting, unused variables and consoles
statements.