Rename rdsr_toshiba_ct_from_dose_images and associated script

rdsr_toshiba_ct_from_dose_images is too long and doesn't fit with the other names.

Renaming it to ct_toshiba to match with ct_philips - it does a lot more than the Philips routine, but essentially the start point and endpoint are the same :-)

Also, the script is not mentioned in setup.py, which presumably meant it wasn't created at install?