[web/test] drop dependency on third party cubes Drop dependency on cubicweb-file, cubicweb-blog and cubicweb-tag for cubicweb/web/test Copy required parts of cubes (schema, entities, views and hooks) into cubicweb/web/test/data/cubicweb-<cube> that make tests pass.

<toc>
  <section resource="add_file" appendto="add_content">
    <title xml:lang="en">Add an attachement</title>
    <title xml:lang="fr">Ajouter un fichier</title>
  </section>
</toc>