Corrected doc'd differences between django-admin and manage.py.

This document outlines all it can do.

In addition, ``manage.py`` is automatically created in each Django project.

``manage.py`` is a thin wrapper around ``django-admin`` that takes care of

several things for you before delegating to ``django-admin``:

``manage.py`` does the same thing as ``django-admin`` but takes care of a few

things for you:

* It puts your project's package on ``sys.path``.

* It sets the :envvar:`DJANGO_SETTINGS_MODULE` environment variable so that

  it points to your project's ``settings.py`` file.

* It calls :func:`django.setup()` to initialize various internals of Django.

The ``django-admin`` script should be on your system path if you installed

Django via its ``setup.py`` utility. If it's not on your path, you can find it

in ``site-packages/django/bin`` within your Python installation. Consider