Add config and object storage for maven packages (11.3 feature)

A maven package repo is shipping in GitLab 11.3 for EEP licenses. https://gitlab.com/gitlab-org/gitlab-ee/issues/5811

Support should also be added here to the charts.

Documentation for Maven Repository Administration

• Have to explicitly enable, with packages.enabled in gitlab.yaml. We need to decide on default on or off. I lean towards on, but this will not work after the default trial has expired unless an EEP license is attached. We'll need to confirm safe fail-off.
• All of these settings will need to be in appConfig, as this will be needed at least in Unicorn and task-runner
• Object storage will need to be configured, and uses Fog configuration as with the rest of the Ruby codebase. We'll need to add a new (and gated) bucket to Minio's defaultBuckets list.