inline the GET request into examples

instead of having it in a before-each
Hydrate ManagedServiceInstance#as_summary_json model spec
Use model's as_summary_json instead of analagous private method
ProvidedServiceInstance#as_summary_json
Do not redundantly nullify service_instances when destroying apps

destroying the service instances is already doing that.
remove service_instances association from app

it should not have been there: see you should not even do a
"app.add_service_instance"
Get rid of update_binding endpoint. The only supported operations for service bindings should be create and delete
Send binding_options to service gateway