STYLE: Refactor vtkITKTransformConverter to consistently template over type

This commit introduces the template function "ReadFromTransformFile()"
allowing to test reading of float or double transforms avoiding
dynamic_cast from "TransformBaseTemplate<float>" to
"TransformBaseTemplate<double>".

It also:

• renames typedefs used for conversion from VTK to ITK to explicitly
  include the "Double" suffix.
• update ReadFromITKv3BSplineTransformFile() function to read ITKv3
  transform as double.

Suggested-by: Matt McCormick <matt.mccormick@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24874 3bd1e089-480b-0410-8dfb-8563597acbee