Replace django-celery

[hackdna]

Django supported out of the box in Celery 3.1.

• Django is now supported in core and new Django users coming to Celery are now expected to use the new API directly (the same library, the same API and the same documentation as everyone else)
• There is no rush to port your existing code to use the new API, but if you would like to experiment with it you should know that (see example project for details):
  • You need to use a Celery application instance
  • You need to explicitly integrate Celery with Django (either configure Celery separately or tell it to use the Django settings)
  • You no longer use manage.py (your app module must store the DJANGO_SETTINGS_MODULE) - need to change Supervisor config and Fabric
• Some features still require the django-celery library:
  • Celery does not implement the Django database or cache result backends.
  • Celery does not ship with the database-based periodic task scheduler.

Requires removing TaskMeta

Release 3.2.2 is the last one and is not compatible with Celery 4.0+, so this is required for #3305.

Remove DB tables used by Django ORM result backend:
manage.py migrate djcelery zero

[ngehlenborg]

While this is fresh in your memory, can you please note here what the dependencies are that led you to update it in #871?

[hackdna]

Basically, django-celery version must match Celery version.

[mccalluc]

#872