Adding plain parameters to demo how to document media types

This adds some plain params and some other narrative documentation to show a couple of ways you could document the JSON requests and responses. The plain params are used to make a table and would also be used to validate requests and responses if a service is fronted by Repose (http://openrepose.org/). Perhaps not all of the plain params are necessary, but I added them for completeness (actually just generated them from the JSON). 

Here's a formatted example (the layout can obviously be adjusted at the xslt level). In html, perhaps the large table might be shown collapsed initially for example.

http://docs-beta.rackspace.com/drafts/david/autoscale-devguide/content/POST_createGroup_v1.0__tenantId__groups_Groups.html