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\173 cookiecutter._env_name \175\175/init.yml" "b/\173\173 cookiecutter._env_name \175\175/init.yml"
index b2d4978..948c765 100644
--- "a/\173\173 cookiecutter._env_name \175\175/init.yml"
+++ "b/\173\173 cookiecutter._env_name \175\175/init.yml"
@@ -2,7 +2,7 @@
 {%- set infra_config_classes = [] %}
 {#- 'global_metadata' is a global collection of objects shared between nodes #}
 {%- set global_metadata = {} %}
-{%- set common_roles = ['_linux_network_interface', '_metadata_process', '_overrides'] %}
+{%- set common_roles = ['_linux_network_interface', '_metadata_process', '_classes', '_overrides'] %}
 parameters:
   _param:
     _esc: $
@@ -31,7 +31,7 @@
           {%- endmacro %}
           {#-#}
           classes:
-          {#- Default roles are added to each node #}
+          {#- Common dynamic roles are added to each node #}
           {#- 'overrides' must be the very last role for each node #}
           {%- for role in node.get('roles', []) + common_roles %}
             {%- include ("{# roles #}/" + role) %}