The way Repositories() was initially called was somewhat different than
other parts of the client bindings because there was no way to instantiate a
Namespace. This change implements a NewRegistry() function which changes
it so that Repositories() can be called the way one would expect.
It doesn't implement any of the other functions of Namespaces.
Signed-off-by: Patrick Devine <patrick.devine@docker.com>
14749fdce4