enable shmVolume setting in OperatorConfiguration (#605)

charts/postgres-operator/templates/configmap.yaml

...ts/postgres-operator/templates/operatorconfiguration.yaml

charts/postgres-operator/values.yaml

docs/reference/operator_parameters.md

manifests/configmap.yaml

manifests/postgresql-operator-default-configuration.yaml

pkg/apis/acid.zalan.do/v1/operator_configuration_type.go

pkg/apis/acid.zalan.do/v1/util_test.go

pkg/apis/acid.zalan.do/v1/zz_generated.deepcopy.go

pkg/cluster/k8sres.go

pkg/cluster/k8sres_test.go

pkg/controller/operator_config.go

pkg/util/config/config.go

pkg/util/util.go