Manage dashboards only for the current datasource

This change adds a new 'datasource' parameter to the dashboard metadata.
This way, the Grafana client state will manage only the dashboards that
match with the deployed datasource (either InfluxDB or Prometheus). For
backward compatibility, the client will always manage the dashboards
that don't set this new parameter.

Change-Id: Iac323d756aff6ca4180f4b648a1d02692ebf292b
2 files changed