0.16.0

• Add compatibility with Grafana 8
• Add Makefile to assist in packaging and publishing
• Overlay image can now be refreshed with the dashboard. Thanks, @jreyesr!
• Revert "Support multiple metrics in popup content for Elasticsearch" again.
  The feature was not ready to be used with PostgreSQL and InfluxDB datasources yet.
• Update plugin name to "panodata-map-panel"