Add array-comma-string for better parsing attributes

This is fix for bnc#903674
Crowbar and/or nova cannot cope with vCenter cluster names containing spaces
https://bugzilla.suse.com/show_bug.cgi?id=903674
Merge pull request #1154 from mjura/array-comma-string-function

Add array-comma-string for better parsing attributes
Fix indentation of exported YAML

When exporting a barclamp that only used the default values from the template
(added_attrs.empty?) the "attributes:" key in the generated YAML was not
correctly indented.
Merge pull request #1156 from rhafer/batch

Fix indentation of exported YAML