OPT: msct_smooth can now calculate 3d derivative with taking real dimensions into account
Merge branch 'augustin' of https://github.com/neuropoly/spinalcordtoolbox into augustin
OPT: changed default z gap from 2 to 15
Merge branch 'augustin' of github.com:neuropoly/spinalcordtoolbox into jca_regMultimodalUsingsliceReg

Conflicts:
	scripts/sct_straighten_spinalcord.py
Merge branch 'augustin' of github.com:neuropoly/spinalcordtoolbox into jca_regMultimodalUsingsliceReg

Conflicts:
	scripts/sct_straighten_spinalcord.py