This change dramatically simplifies the parameter discovery logic in
DefaultApiDescriptionProvider. Instead of surfacing POCO objects as
parameters, we now fully expand every model.
The rationale is that we want to show every key/value that can be set by
the user and not force consumers of ApiDescription to do that themselves.
Tests are cleaned up to match the new behavior.
Hao Kung
Ryan Nowak
N. Taylor Mullen
Kirthi Krishnamraju