Refactor the grafana initialization

[MisterMartin]

Currently we create a CHORDS specific grafana image whose only purpose is to run grafana-cli in order to pre-populate it with plugins. I think I read that you can now do this with a running instance.

So perhaps we can add this to the chords startup script, and ditch the need for our custom image.

[MisterMartin]

If this were done in the chords_start script, then every time that chords was restarted, grafana would have to go out and drag down every plugin. Seems like this would impose an unnecessary startup lag, which would be annoying when doing multiple chords restarts in succession.

We will forget about this for the time being.