Spawns a new subordinate actor of `owner` and stores it in this container.

        jobs = Container()
        ...
        jobs.spawn(self, Job)
        jobs.spawn(self, Job, some_param=123)

        jobs = Container(Job)
        ...
        jobs.spawn(self)
        jobs.spawn(self, some_param=123)

        jobs = Container(Job.using('abc', some_kwarg=321))
        ...
        jobs.spawn(self, extra_kwarg=123)
        jobs.spawn(self, some_kwarg=123, extra_kwarg=123)
        jobs.spawn(self, 'xyz', some_kwarg=345, extra_kwarg=567)

def spawn(self, owner, *args, **kwargs):
        """Spawns a new subordinate actor of `owner` and stores it in this container.

        jobs = Container()
        ...
        jobs.spawn(self, Job)
        jobs.spawn(self, Job, some_param=123)

        jobs = Container(Job)
        ...
        jobs.spawn(self)
        jobs.spawn(self, some_param=123)

        jobs = Container(Job.using('abc', some_kwarg=321))
        ...
        jobs.spawn(self, extra_kwarg=123)
        jobs.spawn(self, some_kwarg=123, extra_kwarg=123)
        jobs.spawn(self, 'xyz', some_kwarg=345, extra_kwarg=567)

        """
        return (self._spawn(owner, self.factory, *args, **kwargs)
                if self.factory else
                self._spawn(owner, *args, **kwargs))