Replace assert statements with appropriate assert* method.
Replace 'assert' with 'assert*' method.
Convert tests.unit.forms.widget_tests to use TestCase class.
Convert bankcard tests to use TestCase.
Convert tests.unit.logging_tests to use TestCase.
Make access check function for dashboard easier to customise
* It can now be specified in OSCAR_DASHBOARD_DEFAULT_ACCESS_FUNCTION
* nav.py and menu.py were split up so that Node can be dynamically
loaded and hence overridden
I recently needed to alter the access function and realised it's not as
easy as I thought.