ivle.webapp.base.rest#RESTView: Remove broken old render() - it should be
                                implemented by subclasses.
                     #JSONRESTView: Remove an impossible assertion, and fix
                                    some exception message spacing.
ivle.webapp.base.test.test_rest: Add a named operation with both default and
                                 non-default arguments, and check that we die
                                 properly when the non-default is unspecified.