Fixes #6608 - expose disk usage info through available_storage_domains API

Fixes #5734 - API for external groups management

Fixes #6844 - display v2 resources rather than v1 resources in /api/v2

Fixes #6446 - Forbidding non-json POST/PUT requests in v2

fixes #6529 allow to define IP suggestion per subnet

fixes #1646, #3103 - enable cloning and locking of templates

Fixes #6532 - permission related api extensions

- usergroups#show lists associated roles
 - listing available resource types
 - filters#show lists associated roles
 - filters#index lists associated roles and permissions and orders the results
 - pagination in permissions#index...

fixes #6003 - don't render user default loc/org object directly

fixes #5631 - API v2 - host and hostgroups show.json.rabl should show all puppetclasses in child node

fixes #5726 - parameter values missing from host#show API call