Upgrade grafana and improve the default configuration, details:

  - Upgrade to Grafana 1.6.1.
  - Make sure we are using StatsD v0.7.1 and not whatever is in master.
  - Ensure that the flushInterval in StatsD matches the retention period expected by Graphite.
  - Add aggregation policies to ensure that max, mins and counts are properly aggregated.
  - Track 50, 75, 90, 95, 98, 99, 99.9, 99.99 and 99.999 percentiles in StatsD.