sct_analyze_texture: use tqdm progress bar, plus some clean-up
sct_analyze_texture: use tqdm progress bar, plus some clean-up


Former-commit-id: 214b93989731de72ef246c8a25bb880bf27cc314
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox