Improves container_tags
Improves container_tags

Changes default queryset to **get_containers_by** all_published.

Simplifies **get_containers_by_channel** query if include_children is
True.

jeanmask/opps,jeanmask/opps,williamroot/opps,opps/opps,williamroot/opps,opps/opps,williamroot/opps,jeanmask/opps,opps/opps,YACOWS/opps,williamroot/opps,YACOWS/opps,jeanmask/opps,opps/opps,YACOWS/opps,YACOWS/opps