Updated directory names and structure based on conversation with Matthijs.
There are now two test directories: pydpiper_testing (for framework py_test scripts) and pydpiper_apps_testing (for testing bits of application code)

Right now pydpiper_apps_testing has one subdirectory (test_scripts) and will have a second directory (test_data) once data is added.
(Git does not like to let you add empty directories to a repository.)