Refact related post to containers migration.
Improve opps.containers admin.

Improves Container admin queryset and redirect objects in
admin to respective child_class edit page.
Merge pull request #410 from jeanmask/stable/0.2.x

Refact related post to containers migration.
Merge branch 'stable/0.2.x' into improve-container-admin

Conflicts:
	CHANGELOG.rst
Merge pull request #411 from jeanmask/improve-container-admin

Improve opps.containers admin.
Update grappelli to ver. 2.4.12
Improve pivot model of Container related.

Removes field options "blank" and "null", for improves database consistency and queryset avoiding "LEFT JOIN" and enable referecial integrity when Containers are deleted.
Merge pull request #412 from jeanmask/improve-container-admin

Improve pivot model of Container related.
Merge pull request #413 from jeanmask/update_grappelli

Update grappelli to ver. 2.4.12
Merge branch 'stable/0.2.x' of github.com:opps/opps into container_queryset_multchannel
merge draft version, @jeanmask

* 'stable/0.2.x' of github.com:opps/opps:
  Improve pivot model of Container related.
  Update grappelli to ver. 2.4.12
  Improve opps.containers admin.
  Refact related post to containers migration.

Conflicts:
	CHANGELOG.rst