Refactoring of the test runner to use the django-discover-runner & cleanup of code coverage script

The test suite now uses the standard django test runner with django-discover-runner to discover all tests.
I changed the convention of filenaming to the default convention of unittest2 test_*.py.
It can be configured in any way you wish it to be.
Also I cleaned uo the code coverage script and added an option to include an xml report as well.