[1.6.x] Documented how to rename get_query_set if you are a library author

Methods that return a ``QuerySet`` such as ``Manager.get_query_set`` or

``ModelAdmin.queryset`` have been renamed to ``get_queryset``.

If you are writing a library that implements, for example, a

``Manager.get_query_set`` method, and you need to support old Django versions,

you should rename the method and conditionally add an alias with the old name::

    class CustomManager(models.Manager):

        def get_queryset(self):

            pass # ...

        if django.VERSION < (1, 6):

            get_query_set = get_queryset

        # For Django >= 1.6, models.Manager provides a get_query_set fallback

        # that emits a warning when used.

If you are writing a library that needs to call the ``get_queryset`` method and

must support old Django versions, you should write::

    method = getattr(some_manager, 'get_queryset', some_manager.get_query_set)

    method(params)

``shortcut`` view and URLconf

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