Export pools as Rundeck "Resource Model Source"

Rundeck documentation for URL resource model sources:
* http://rundeck.org/docs/manpages/man5/resource-v13.html

Axemblr Provisionr URL:
* http://localhost:8080/rundeck/machines.xml
Merge pull request #138 from andreisavu/issue-138

Export pools as "Resource Model Source" for Rundeck