fixes #2810 - more restful API v2 JSON responses in puppetclasses

NOTE: breaking changes to API v2 api/lookup_keys does not exist, replaced by api/smart_variables and api/smart_class_parameters
fixes #3011 - default root node name for api index json response to :results but make it configurable
fixes #3011 - changes to rabl templates and tests since root node defaults to 'results'