Add exclude argument to VUnit cli

[remvb]

I would like to add a CLI argument that allows users to exclude some testcases, while still running all the other cases. This would still be compatible with the already implemented test_patterns.

For example:
python run.py <testcases-to_run> --exclude <testcases-to-exclude>

This feature would be helpful to me and I imagine this could also help others.

I have a clear idea on how to implement it, but I am wondering how I should be tested it properly. Should this be integrated into the already existing test_filtering_tests function in test_ui.py; which tests the attribute arguments. This would be an extension of this function that properly tests the combination of test_pattern, --exclude, --with-attribute and --without-attribute.
Or should it be a separated into a new testcase in test_ui.py.
I am personally in favor of expanding the test_filtering_tests function as these 4 arguments affect the test list. Are there any other tests that should be modified or added to test this new feature?