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Added the ability to edit or delete comments. Also added the ability to
preview comments (like django.contrib.comments does) and confirm deletion of
comments.
Also fixed a few bugs, one which was major and made it so that redirection
worked improperly after a new ThreadedComment was posted.
Finally, added max_depth as an attribute to the moderation system, so that
someone cannot vandalize the system by posting a long series of replies to
replies.