This is cleaner and makes more sense since there are only 2 modes
of indexing root cells: either IIK or KJI. It is not considered
that any other one would be potentially useful for anything.
So I am either transposing the default (i.e., VTK-style, that is
x-axis minor and z-axis major) to the x-axis major and z-axis
minor used by some applications.

Change-Id: Ic79f23622402c9579eefd57ea09743fb72788aa2