Section was picking up the size of children elements. With relative it 
works.

The inline style makes problems with fixed sized elements in dynamic 
sections.

This change needs to be reviewed thoroughly.

This allows elements in dynamic sections to have fixed dimensions.

Some modifications to property panel logic, to show dimension fields and
proper labels.

Only implmented in dropList and button elements.

The child elements are created directly in the component when reading a 
serialized cloze.

The whole parsing process of cloze elements will be reworked soon. So 
this probably is a temporary fix.

Fix a problem when saving compound children

see https://github.com/iqb-berlin/verona-data-specifications/blob/main/responses/manual_iqb-standard.md

The entire HTML is no longer saved, but only the indices and the color
of the markers

- Use the same default state for interactiveMuteControl
and for playerProps.interactiveMuteControl

Use a suffix button to activate color picker instead of having an extra 
form field.

Also add direct input for likert line coloring color.

Options still had a margin-top, which is wrong when there is no label 
above.

Fix typo

The theme file is now project specific because Angular demands assets
to be part of the project.
It also differs in content: The editor theme is only applied to canvas
elements. For the player every checkbox and radio button is affected.

The components now again use the default color of 'accent'. The custom
theme now has the green as accent color and no longer primary.

Used in checkboxes and radio buttons, which are now green.
The secondary is unused but for safety set to the same as the default
theme should be.

This new setting makes child items space around in a row with line 
break.

Images in vertical alignment now always reserve the whole row and don't 
appear next to each other.

- Rename NumbersKeyboardComponent to MathKeyboardComponent
- Decrease the number of input properties
- Split source code into private methods

Use unit field of UnitService directly to detect changes.

- Ignore blank pages when calculating the response progress

- Replace onClick method with an event emitter inside the template

Remove useless plugin and add rule overrides for e2e test dir.

Variable naming, reorder imports etc.

Introduce interfaces and clean the structure.

This makes for cleaner imports.

The dropListList generation is now done when things are changed via the 
section menu and no longer on element update via unit service.
Also remove some interfaces to avoid circular imports. The interfaces 
are so small and insignificant that their form might as well be 
specified at usage point.

No longer have unit as subject. Components can use the unit variable as 
is and still get updated.
This removes some listener stuff in conected components.

Was not correctly creating new instances of non-primitive values. Now
uses "JSON.parse(JSON.stringify(element))" for deep copying the element
first.

Also refactor by moving the method to the UnitService, where all ID
handling should take place.

No longer is a singleton but a normal servicce now again. The singleton 
logic was needed in the past but not anymore.

Generally only the editor needs to generate new IDs. Before there was
need to have it in common because some elements (like compound elements)
needed to generte new Elements including IDs.
Now all ID stuff is handled by the UnitService and the elements classes
are handed the fully built elements. Unfortunately this means that some
logic has to move back from classes into the UnitService. To un-bloat
the UnitService a (and in the future some more) helper class is created
for this logic.

The most important thing is, that the UIElement no longer generates
an ID when created. The ID has to be created before and passed to the
constructor.