Patch courtesy of david@zettazebra.com, adds the ability to add tags to
tickets if django-tagging is installed and in use. If django-tagging isn't
being used, no change is visible to the user.
Add rudimentary CC: functionality on tickets, controlled by staff users. CC's
can be e-mail addresses or users, who will receive copies of all emails sent
to the Submitter. This is a work in progress.
