(dup issue) The domain of solid:owner should be more open than Storage

[timbl]

We use solid:owner to specify the owner of a pod. But there seems to be be reason to restrict it in the ontology to be as specific as a Storage. I'd like to be able to use it elsewhere internally for things like folders and files within the pod ... or bots for that matter maybe also.

Suggest remove the domain constraint on solid:owner

(Sorry I missed the discussion in the previous PR)

I may want in my code to do things like

{ ?doc pod: ?storage .    ?storage solid:owner ?x } => { ?doc solid:owner ?x }

OWTTE

[timbl]

Dup of #265