In fact, make changes in common to let the player understand the slider component.

It needs row and column to work. (It is using flex in the background.)

Use 'horizontal' and 'vertical'. Which are better terms and also align 
with other element's values.

Also improve conditional border style. The additional dragPreview is 
needed so the dragged item does not have the border.

In the UI. Internally it is still likert.

The player-element dialog options did not show the field, even when it 
has a value. Now it properly checks of the existing config has this set.

This element has a list of string as editable options. Those strings 
form draggable elements which may be reordered or moved between 
different DropList elements.

Also refactor option change logic to allow any property not just the 
text property.

It logically belongs there since it is no compound element and also 
needs to be near the other radio group.

Now correctly shows a dropdown instead of a text area.

This works similarly to the standard radio group, but has a fixed 
horizontal layout with images above the options.

When selecting the preset value, sometimes the string is empty and it is 
not possible to differentiate the options. Therefore an index is added 
making it possible to reliably select a value.

The whole panel tab was not correctly checking for value existence. Need 
to check for undefined not null.

Function was incorrectly returning after the first element.

There were some things missing when renaming questions/answers to 
rows/columns. Now everything is properly named.

This function will be implemented differently.

To not have the same name as likert rows and cause issues on the props 
panel.

- Use ngModel so it returns number

This allows setting up a specific color, which might be harder to find 
in the color picker. Also allows setting 'transparent'.

The icon does not make it sufficiently clear what the purpose is.