purge "purge"?

[mccalluc]

It was used for the old container management, but it's been replaced by LRU. Confirm that Refinery doesn't need it before removing.

For example, tasks.py:

@task()
def django_docker_cleanup():
    # TODO: Specify manager, if not default
    DockerClientWrapper().purge_inactive(
        settings.DJANGO_DOCKER_ENGINE_SECONDS_INACTIVE
    )

@jkmarx and @scottx611x : Opinions?