INST: improved management of version.txt
INST: improved management of version.txt

Former-commit-id: 682084556cd846ce1d2a2a46134b3f5b1c7f091a
Former-commit-id: f0e2a261d626958c70d8bdcee9919b91f7c779a3
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox