This function will be implemented differently.

* Refactor markable text
* Prevent multiple selections (feature is only supported in Firefox)

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'.

* Use IntersectionDetector for intersectionDetection directive
* remove unnecessary input 'index' from page component

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

The condition did not respect the case of null value.

This is necessary to reset elements like radio button group. We use null 
for that instead of undefined.

The check was in place before to make sure input fields only accept 
valid values (no text in a number field for example). Angular thinks a 
null value is valid so we have to do this extra check. This is now done 
directly in the template before calling the updateModel method.

The outline needs some space outside the element. This space may be more
than the parent has (when the element is positioned right at the edge).
When this happens we simply ignore that 1 pixel space. Everything still
shows correctly.

And avoid global styling.

This way empty paragraphs still produce an empty line.
Not possible to do inline because CSS pseudo classes do not work inline.

This way the color-input element can read the color and show the correct 
preview.

This needs a z-index on the selected section, since the outline collides 
with other sections and is not shown on this side.

Was missing margin at the top.

Put the buttons to the right side instead of in the middle somewhere.

Make radio button and first line of the label (in case there is a line 
break) appear at the same height.

This makes it so that other options appear with strikethrough when one 
is selected.

Other components will follow.