Update Debian packaging to use the new configuration directories

Update Debian packaging to use the new configuration directories

This updates the Debian packaging to use the new configuration
directories introduced by
https://github.com/tvheadend/tvheadend/pull/1535 and
https://github.com/tvheadend/tvheadend/pull/1538.  Instead of being
in /home/hts/.hts/tvheadend, the configuration will now be stored in
/var/lib/tvheadend by default, which is consistent with how many
other "server"-style Debian packages handle their home directories
and configuration.