[media] doc-rst: backward compatibility with older Sphinx versions

Sphinx is really evil when an older version finds an extra
attribute for the :toctree: tag: it simply ignores everything
and produce documents without any chapter inside!

As we're now using tags available only on Sphinx 1.4.x, we
need to use some creative ways to add a title before the
table of contents. Do that by using a css class.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>