Put all language versions under ustar_cp directory

[dorchard]

From discussion with Gilberto, the best thing going forwards for delivering this work is to have the development all inside the ustar_cp directory and that we conclude things having a ustar_cp/matlab and ustar_cp/python directories (which would allow people to be able to switch between the two and build up trust/confidence in the new Python approach); and in the transition we can have ustar_cp/matlab_refactor_wip moving what is currently ustar_cp_refactor_wip.