Instructions for importing Grafana dashboards and datasources into existing Grafana instance

[arlake228]

• One part of this is just pointing psconfig-grafana-agent at your instance. Instruction will be about create auth token in grafana and applying URL+token using psconfig agentctl grafana ...
• Open question whether other dashboards need to import. We can export dashboards in such a way that the user selects the data source. Likely don't want separate copies to maintain with the datasource cleared out. Could just maintain a public instance from which peopl can export? or somehow automate tthe generation of the exported version? Maybe just say "find a perfsonar instance and here is how to export"/