Create Django apps with models, URLs, and view stubs

* Keep `core` app small (with no UI, and just the ubiquitous `User` and `Group` models)
* Create topic-specific apps for handling groups of models and the URLs that service them
* Name all URLs (usually the view name)
* Create view stubs for all URLs and import where referenced
* Create stubs for decorators and import where referenced
* Add apps to `settings.LOCAL_APPS`
* Distribute all models from `doc/draft-models.py` and all URLs from `doc/draft-urls.py`