BUG: Fix unit scaling change

A scale of 0 could be generated when changing from one scale to another
(e.g. 0.1 to 1.)

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23206 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Apply units to Transforms module

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23207 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Automatically select the correct unit singlestep

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23208 3bd1e089-480b-0410-8dfb-8563597acbee