Fixed #18261 -- Clarified 'project root directory'

These files are:

* The outer :file:`mysite/` directory is just a container for your

* The outer :file:`mysite/` root directory is just a container for your

  project. Its name doesn't matter to Django; you can rename it to anything

  you like.

* The inner :file:`mysite/` directory is the actual Python package for your

  project. Its name is the Python package name you'll need to use to import

  anything inside it (e.g. ``import mysite.settings``).

  anything inside it (e.g. ``mysite.urls``).

* :file:`mysite/__init__.py`: An empty file that tells Python that this

  directory should be considered a Python package. (Read `more about

The script should be run from one of two places:

* The root directory of your Django project.

* The root directory of your Django app.

* The root directory of your Django project (the one that contains

  ``manage.py``).

* The root directory of one of your Django apps.

The script runs over your project source tree or your application source tree

and pulls out all strings marked for translation (see