Delete devlog entries when deleting pages

[hannesbochmann]

devlog entries can be on every page. non-admins shouldn't see those entries but they still should be able to delete pages with devlog entries on them. By default this won't work as they need table modify access.

Therefore the deletion of devlog entries should be done before deleting the page without checking access.

[hannesbochmann]

devlog entries are no longer copied along when a page is copied even not for admins.
devlog entries are deleted before a page gets deleted without checking the permissions.