add openshift customizations, templates, and test (#871)

- It modifies the Dockerfile and entrypoint slightly to allow for OpenShift SCCs to operate correctly
- It adds 2 template examples that can be easily modified by changing parameters

Fixes #572

kubernetes/patroni_k8s.yaml

@@ -36,6 +36,8 @@ spec:
           valueFrom:
             fieldRef:
               fieldPath: metadata.namespace
+        - name: PATRONI_KUBERNETES_USE_ENDPOINTS
+          value: 'true'
         - name: PATRONI_KUBERNETES_LABELS
           value: '{application: patroni, cluster-name: patronidemo}'
         - name: PATRONI_SUPERUSER_USERNAME