ssdp-responder v2.1

Changes

• Add support for JSON output with ssdpd-scan -j, issue #17
• Dump received data from devices in ssdp-scan -l debug
• Termios support for disabling ^C output from ssdp-scan
• Update copyright years, LICENSE file hash change
• Source /etc/default/ssdpd from systemd unit file

Fixes

• Fix #15: add fallback to /var/lib/ssdpd/uuid.cache
• Fix #16: truncated UUID when reading from cache file