STYLE: Use vtkNew in vtkSeedTract/vtkDiffusionTensorGlyph/...

This commit simplifies code using vtkNew where it makes sense.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23698 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Simplify vtkSeedTracts::TransformStreamlinesToRASAndAppendToPolyData

This commit updates the function to use vtkNew and simplifies the code
by removing redundant calls.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23699 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Simplify vtkMRMLFiberBundleNode::Add(Line/Tube/Glyph)DisplayNode methods

This commit update the functions Add(Line/Tube/Glyph)DisplayNode methods
to return null if no scene has been set. Doing so will prevent memory leak
ensuring new node are always added to the scene.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23700 3bd1e089-480b-0410-8dfb-8563597acbee