Comply with spec for permissions needed to delete a resource

Basically, until https://github.com/solid/web-access-control-spec/issues/47 gets discussed with a proper decision process, let's undo what was done in https://github.com/solid/node-solid-server/issues/729.

I'm not so fussed about the actual behaviour, I just want to start the process of documenting what we consider the spec (see also https://github.com/solid/solid-spec/issues/174), and on which points we are aware of differences between NSS and the spec.

Wherever such differences exist, if we think that NSS is right, then we should update the spec.
And if we think the spec is right (like in this case), we should (at least create a github issue to) fix NSS.

PS: If anyone is aware of any other points on which NSS is not spec-compliant, then let's create issues for each one of those. We can decide to willingly leave NSS broken, but at least we should have github issues that document how NSS is broken.

Beginne mit dem Lesen des verknüpften Issues 47 in web-access-control-spec, des NSS-Issues 729 und des solid-spec-Issues 174, um die Berechtigungsanforderungen für das Löschen einer Ressource zu vergleichen. Im Issue sind keine Dateien oder Tests genannt; als abgeschlossen gilt die Dokumentation des Unterschieds zwischen NSS und spec sowie die Festhaltung der Entscheidung, mit einem nachfolgenden NSS-Issue, falls sich die Implementierung ändern sollte.