access and usage constraints

in the sample i noticed this section on constraints:

```
accessconstraints: otherRestrictions
```
This seems inspired by how things are done in ISO19115, unfortunately ISO also is not quite optimal.

More important then access constraints is under which conditions/license the work can be (re)used (CC0, CC-BY, ...) (legal-usage-constaints?).

`otherRestrictions` is not a proper value by itself, in iso it is usually combined with a second statement to indicate what the other restrictions are.

```xml

No limitation



```

If accessConstraints are enforced, it is interesting to state the reason why public access is limited; INSPIRE suggested [this codelist](https://inspire.ec.europa.eu/metadata-codelist/LimitationsOnPublicAccess) with relevant argumentation