Copying over cffi_ros_utils for cram-highlevel

The ```cffi_ros_utils``` only depends on 3rdparty libs ```split-sequence``` and ```cffi```, and provides utilities to use ```cffi``` in a ROS environment. I think it fits better into ```cram_3rdparty``` than into ```cram_highlevel```, even though it is technically not a 3rdparty library.