add ec:replaces for Resource (just like for Asset)

[wivaku]

In the schema an Asset can be replaced by another.
It would make sense if a Resource can also be replaced by another.

ec:Resource
...
[
    a owl:Restriction ;
    owl:onProperty ec:isReplacedBy ;
    owl:allValuesFrom ec:Resource
  ], [
    a owl:Restriction ;
    owl:onProperty ec:replaces ;
    owl:allValuesFrom ec:Resource
  ],```

[tormodv]

No, the fact that something replaces something else is an editorial decision, and the metadata of the operation is stored in an EditorialObject.
Each Resource have an editorialObject, or subclasses thereof, describing it.

See #501