Prevent Debian package upgrades from prompting.

Prevent Debian package upgrades from prompting.

Before, we were using dpkg "conffiles" for our configuration.  This means
that if the admin has customized the configuration (as is necessary to
make the switch work) and the default configuration included in the package
changed, then dpkg would prompt the user interactively about what to do.

Now, we take responsibility for creating, upgrading, and removing the
configuration file ourselves, and do not prompt.