The urls must be declared as trusted to be accepted by the application.

The latest change to page width and ratio needs to be reflected by a 
version change.

When this is set the page will only be rendered to that width. Otherwise 
100% of the available space is used.

This property should be used when an always visible page is used and 
states the ration of the always visible page to the other pages.

This is made for any warn message properties, which only appear when the 
corresponding velidator is actually used.

NgModel is needed so the value returned frim the field in number instead
of string.

Fix bug

* in eager mode a vopStateChangedNotification is still sent
* otherwise the last state is cached in the `VeronaPostService` and
can be retrieved from the host

Use global style for droplist cursor.

In this mode sections can be inserted, reordered and deleted with 
buttons directly on the canvas.

When form changes the `responseProgress` is determined and sent

Intersection detection is done by `Intersectionobserver`

In the past, the page index could be set by button click and after
scrolling, which led to unwanted side effects

To center the content of the player, the dimensions of all pages are
calculated.

Before it was the index of the option. HTML UI Elements take the actual 
value as parameter anyway so no need to use any index.

Remove unused stuff, add comments.

The section now always has the same width as the page (minus margin).

The new name is shorter and clearer.

Relevant for drowdown and radio button group.

Can only be true/false.