Retrieving anonymous properties in ArtifactShapeSchema

In standard `ArtifactShapeSchema` anonymous properties aren't retrieved.
Example data
```turtle
ex:AddressShape
    a sh:NodeShape ;
    sh:closed true ;
	sh:targetClass ex:Address ;
    sh:property [
        sh:path ex:streetAddress ;
        sh:datatype xsd:string ;
    ] .
```
This way of writing is commonly used to to define properties "near" their shape