[fix bug 820747] [fix bug 820398] Enhance 'Users' and 'Groups' Admin panel.
Update (django-)celery.
Merge pull request #370 from glogiotatidis/820398

Admin panel enhancements
Install celery and django-celery in vendor-local.
Update celery and djcelery to 2.5.5
[fix bug 819214] Add Simplified Chinese (zh-CN).
[fix bug 811799] ExactTarget support.
Merge pull request #371 from glogiotatidis/basket

[fix bug 811799] ExactTarget support.