PMM-1996 Change of manual file URL

PMM-1773 Add Grafana metrics.

PMM-1773 Add Grafana metrics.

Merge pull request percona#40 from percona/PMM-1874-proxy-read-timeout

PMM-1874 Increase proxy read timeout.

PMM-1830 handle Read timed out issue correctly

PMM-1771 create pmm-managed db during docker update

PMM-1732 enable etag in nginx

PMM-1441 map /managed/ to pmm-managed endpoint

PMM-1441 map /managed/ to pmm-managed endpoint

use percona-prometheus-1.7.1 for PMM 1.3.2