The unit test module path is now accepted as a command line option. This brings more capabilities
of Gary Thompson's test_suite/unit_tests/unit_test_runner.py script into the relax command line.
The _pipe_control/test_value unit test module path can be specified as, for example, one of
'test_suite.unit_tests._pipe_control.test_value', 'test_suite/unit_tests/_pipe_control/test_value',
'_pipe_control.test_value', '_pipe_control/test_value'. This allows individual modules of tests to
be run, rather than having to execute all unit tests, which is very useful for debugging.
