docs: set up for release documentation. Make changes to publish security.html with CVE announcements referring to the sections in upgrading.html rather than CVE.html. Remove templates.zip as part of html build in Makefile. Also update doc for using CVE.html.

License
=======

Roundup is Free Software under the following license (from the
file COPYING.txt in the software distribution):

.. raw:: html

   <div class="file_insert">

.. include:: ../COPYING.txt

.. raw:: html

   </div>