read configs from /etc/ddr/ddr.cfg and /etc/ddr/local.cfg

Values in local.cfg override values in ddr.cfg.
rm dangling MEDIA_BASE symlinks; better logging

In certain cases where the target for the /var/www/media/base
symlink is removed  (e.g. USB drive unmounted) without removing
the symlink, and a different store is mounted, the dangling
link needs to be removable.