ENH: Use VTK to write VTK files
BUG: replace baseline files with correct ones.

I enhanced the CompareFibers program to a) use VTK readers
and b) traverse the vtkPolyData objects returned and
actually compare all the fiber tracking data.

This actually broke the tests, because the files
generated by the current version of UKFTractography
has different data in them than the existing
baselines.  The actual fiber points are the same,
but the 'decorative' data is different.
ENH: Add a new test for writing out XML data files.

enhanced the test program to detect file type (just by the extension
so far) and use the appropriate reader type.
COMP: unified vtk file writing.

Use a single function to write out vtkPolyData
if the file extension is vtp, use the
vtkXMLPolyDataWriter.
ENH: Add ConvertVTK Utility

ConvertVTK will convert any VTK PolyDat file
in legacy or XML format to any other
VTK polydata format.
Merge pull request #2 from BRAINSia/FixVTKWriter

Fix vtk writer