Begin modeling the packaging metadata

Includes:
  * Classifier
  * Project
  * Release (without dependency information)
Upgrade djorm-ext-pgarray to >= 0.5 which works with Python3
Fix Classifiers so that they can be unique in the database
Flesh out the admin interface for warehouse.packaging
Replace the conversion SQL with a script
Add a script to upgrade a user to a superuser
Remove obsoleted fields some which will be replaced
Simplify the Contact models to remove duplication
Store the description, license, and changelog

Use a related model with a OneToOneField to represent each
document.