The AWS CLI SG commands are not necessary, kops creates an SG with these ports open to the correct SG by default

This updates prometheus to 1.7.1 where it was missing

Removed grafana restart comment from doc, as it's not necessary (grafana-watcher should pick up the changes and reload the dashboards).

Added some comments to the doc, to:
- Point the directory where make generate should be executed from
- Mention that the dashboard file should be suffixed with "-dashboard.json".
- Added hints to apply the new configMap and restart grafana

git-subtree-dir: contrib/kube-prometheus
git-subtree-mainline: 050ca21276696c8603375c699513ec487301ed62
git-subtree-split: 81c0d2f4