Replace statefulset.yml with Helm chart

[snpdev]

This is a sub-issue of https://github.com/amazeeio/lagoon/issues/564#issue-350184516, bullet 7:

7. Create more OpenShift Objects (Deployments, PVCs) based on the figured out services (happens in https://github.com/amazeeio/lagoon/blob/master/images/oc-build-deploy-dind/build-deploy-docker-compose.sh#L365-L495)

This issue specifically concerns the replacement of the StatefulSet OpenShift Template with a Helm chart.

# Generate statefulset if service type defines it
    OPENSHIFT_STATEFULSET_TEMPLATE="/oc-build-deploy/openshift-templates/${SERVICE_TYPE}/statefulset.yml"
    if [ -f $OPENSHIFT_STATEFULSET_TEMPLATE ]; then
      OPENSHIFT_TEMPLATE=$OPENSHIFT_STATEFULSET_TEMPLATE
      . /oc-build-deploy/scripts/exec-openshift-resources-with-images.sh
fi

https://github.com/amazeeio/lagoon/blob/master/images/oc-build-deploy-dind/build-deploy-docker-compose.sh#L594-L599

[snpdev]

Closing. We are not creating a Helm chart for each K8s resource. Rather, we will have a Helm chart for each service, e.g. Varnish.