rename cluster levels to non-underscore names

Change-Id: Ic9bdafbeb1333699ce424612f8b2e8d8dafb7be2
diff --git a/classes/cluster/sl-k8s-calico/init.yml b/classes/cluster/sl-k8s-calico/init.yml
new file mode 100644
index 0000000..eca25ff
--- /dev/null
+++ b/classes/cluster/sl-k8s-calico/init.yml
@@ -0,0 +1,5 @@
+classes:
+- cluster.sl-k8s-calico.kubernetes
+- cluster.sl-k8s-calico.stacklight
+- cluster.sl-k8s-calico.infra
+- cluster.overrides