Switching a page to versioned/unversioned should copy the whole page and be tracked in history

When switching a page to unversioned/versioned, the whole page should be copied.

Currently, only the content is, which loses all other important data: attachments, comments, tags, objects, history. After this copy, the relevant object for the book extension should be modified/added/removed.

This switching process should also be tracked in the history, for instance: "Page has been changed to unversioned from Version X"