Removed MEDIA_ROOT/URL from default settings template.

Many sites will never deal with user-uploaded files, and MEDIA_ROOT is
complicated to explain.

Thanks Carl Meyer for the suggestion.
Removed STATIC_ROOT from the default settings template.

It isn't necessary in development, and it confuses beginners to no end.

Thanks Carl Meyer for the suggestion.
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.

Thanks Jacob Kaplan-Moss for the suggestion.