Our new recovery.conf generation procedure doesn't create trigger files,
so we should only document pg_ctl usage.

Additional recording rules for improving dashboards speed.

Include the example rules from the node_exporter[0].

[0]: https://github.com/prometheus/node_exporter/blob/master/example.rules

1. Moved from hours to seconds
2. Fixed some typos
3. Humanize output

1. using fqdn instead of instance will be better
1. humanize value output