Fix display of the Delete button on a document when missing permission on the parent

The Delete icon/button is displayed on the current document if the current user has the Remove permission.

However to be able to delete a document, one needs the Remove permission on the current document but also the RemoveChildren permission on the parent.

So a second test on the parent must be added to the isAvailable method at https://github.com/nuxeo/nuxeo-ui-elements/blob/maintenance-2.4.x/actions/nuxeo-delete-document-button.html#L117

It would probably require that the permissions are computed for the first accessible parent.

 PS : the code of this method for master is different and is testing "Write", which is not good: https://github.com/nuxeo/nuxeo-ui-elements/blob/master/actions/nuxeo-delete-document-button.js#L114