RegistryManager creates a new registry context for the registration of StackedObjectProxy instances. Multiple RegistryManager's can be in a WSGI stack and will manage the context so that the StackedObjectProxies always proxy to the proper object.

The object being registered can be any object sub-class, list, or dict.

Registering objects is done inside a WSGI application under the RegistryManager instance, using the environ['paste.registry'] object which is a Registry instance.