Added model examples, unit tests

Check out our new model examples page. Each example there features one or more models, with example API usage.

This is intended to be a repository of common cases -- how to use many-to-one relationships, many-to-many relationships, etc. We'll be updating this frequently with more examples.

The coolest thing here: This documentation is automatically introspected from our brand-new model unit tests. To run the tests, run "runtests.py" in the "tests" directory of the Django distribution.

Posted by Adrian Holovaty on July 29, 2005