Users can now configure whether they want the default tagging options enabled (tag `latest` for the default branch, and tag with the git branch or tag name), and can also specify custom tags, including static tags and dynamic templated tags.
Fixes https://jira.coreos.com/browse/QUAY-1747
This change replaces the metricqueue library with a native Prometheus
client implementation with the intention to aggregated results with the
Prometheus PushGateway.
This change also adds instrumentation for greenlet context switches.