Fix rotation handling in vtkTransformInterpolator.

Overhaul the handling of rotations in vtkTransformInterpolator, which
was being done in a completely wrong manner due to performing
interpolations on angle-axis rotation values rather than actual
quaternions.

Change-Id: I593a2a8baeeab4b3734cbaece99dbe5da497fe98
Fix operation order in vtkTransformInterpolator.

Modify vtkTransformInterpolator::InitializeInterpolation() to set the
interpolation type first, then initialize the interpolators, AND THEN
set the number of tuples. The quaternion interpolator may not care, but
for vtkTupleInterpolator, this ordering is CRITICAL, as either of the
first two steps may unset the number of tuples, resulting in a broken
interpolator.

Change-Id: Id4787bb304ca4b3e8a9501e5583b4caf59dd507f
Merge topic 'fix-transform-interpolator' into master

192ddaaa Fix operation order in vtkTransformInterpolator.
980d6488 Fix rotation handling in vtkTransformInterpolator.