Enhancement: Public link permission `PublicLink.Write.all`

Support for the public link permission `PublicLink.Write.all` has been added. Users without this permission won't be able to create public links (except for oC10 instances where this permission is being set implicitly).

https://github.com/owncloud/web/pull/8541
https://github.com/owncloud/web/pull/8796
https://github.com/owncloud/web/issues/8540
