[Improvement] Add Prometheus and Grafana in Helm Chart

[unknowntpo]

At #56 , we haven't added Prometheus and Grafana to helm chart yet, so we plan to do it at this Issue.

Tasks:

• Add init/grafana/init.sh, init/prometheus/init.sh, it will use sed to inject host name of other service into config files (similar to init/hive/init.sh)
• Add helm templates prometheus.yml, grafana.yml in ./helm-chart/templates
  • We can simply use hostPath Persistence Volume to mount config file of Prometheus and Grafana into pods.
• Add corresponding values at values.yml
• Modify ./helm-chart/templates/NOTES.txt, add description about these two services.