Include namespace in URL name

When using ``show_urls`` the namespace wasn't part of the output:

    python manage.py show_urls -f table

    URL      | Module                             | Name         | Decorator
    ---------+------------------------------------+--------------+-
    /        | project.myownapp.views.Home        | home         |
    /admin/  | django.contrib.admin.sites.index   | index        |
    ...

This resulted in the inconsistent behaviour where you could use ``{% url 'home' %}`` in a template without any problems, but using ``{% url 'index' %}`` would result in the template error `Reverse for 'index' with arguments '()' and keyword arguments '{}' not found.`.

This changeset fixes that by including the namespace in the output of ``show_urls``:

    python manage.py show_urls -f table

    URL      | Module                             | Name         | Decorator
    ---------+------------------------------------+--------------+-
    /        | project.myownapp.views.Home        | home         |
    /admin/  | django.contrib.admin.sites.index   | admin:index  |
    ...

Caveat emptor: The change was made without intimite knowledge of how Django determines where a request should end up.  I did take a small peek at ``django.core.urlresolvers`` though.