Add new node attribute 'classes:'

'classes:' allow to attach additional classes from 'system'
and 'service' models; or from 'cluster' model in the following
format:
          - cluster.${_param:cluster_name}....

Change-Id: I357c5ed3f06d666a4c5f9e7318d651c404eca139
diff --git "a/\173\043 roles \043\175/_classes" "b/\173\043 roles \043\175/_classes"
new file mode 100644
index 0000000..34a02f5
--- /dev/null
+++ "b/\173\043 roles \043\175/_classes"
@@ -0,0 +1,12 @@
+{#-
+parameters:
+  reclass:
+    storage:
+      node:
+        <reclass_storage_node_name>:
+          classes:
+           # list of extra classes provided from the context file
+#}
+          {%- for class in node.get('classes', []) %}
+          - {{ class }}
+          {%- endfor %}
\ No newline at end of file