Used an absolute path for the SQLite database.

This ensures the settings file works regardless of which directory
django-admin.py / manage.py is invoked from.

BASE_DIR got a +1 from a BDFL and another core dev. It doesn't involve
the concept of a "Django project"; it's just a convenient way to express
relative paths within the source code repository for non-Python files.

Thanks Jacob Kaplan-Moss for the suggestion.
Added security warnings for the most sensitive settings.
Adjusted the default URLconf detection to account for the admin.

It's now enabled by default.
Updated tutorial 1 for the new project template.
Updated tutorial 2 for the new project template.
Minor fixes in tutorials 5 and 6.
Documented the simplified app & project templates in the changelog.