Merge pull request 3scale#466 from srijitamukherjee/Grafana-Dashboard

Added Sidekiq metrics to System Grafana Dashboard

Merge pull request 3scale#408 from 3scale/remove-metering-labels

Metering labels validate label max length

General Availability Release of 3scale 2.8.1

General Availability Release of 3scale 2.8.0, containing extra docs f…

…ixes from image produced in 2.8.0 advisory - commit c4532a0