re #9421 Restructured the test folder
re #9421 Added unit tests for resend_cached_payload() and send_data(); moved api_client.py into usb_detector package
re #9421 Added unit tests for client_set_config(), cache_failed_payload(), and read_connected_devices()
re #9421 Added unit tests for update() - usb detector and usb_detector_set_config()
re #9421 Added unit tests for notify_listeners() and register_listener()
re #9421 Added unit tests for get_metadata() and send_payload_to_server()
re #9421 Added unit tests for get_connected_devices() and get_disconnected_devices()
re #9420 Created folders src and tests