Integration: Grafana template

[eledhwen]

Consider the creation of a proper Grafana template that we can reuse on new projects (instead of copy/pasting from a given project).

Explore avenues for keeping a dashboard up to date without compromising local tweaks (not possible AFAIK, but maybe there are some best practices out there).

Important focus points for this issue include:

• design an application-specific dashboard (pretty much identical to the ones used at geopost)
• having re-usable a dashboard JSON description in a /grafana directory
• make sure the dashboard works properly with varying sampling frequencies

Extension points:

• design a cross-application / high-level overview dashboard for monitoring activity across multiple services (less emphasis on knowing exactly what does / doesn't work, more emphasis on detecting service level dysfunction)

[eledhwen]

Can be impacted by #23