New vessel branch extraction module for 3D Slicer

We added a new module to 3D Slicer's SlicerVMTK extension for much faster and flexible vessel centerline extraction. This video demonstrates the followings:
- Vessel segmentation
- Vessel centerline extraction
- Centerline curve editing
- Curved planar reformatting (straightening)
- Centerline extraction and quantification for multiple branches

All tools are free, open-source:
- 3D Slicer (https://download.slicer.org)
- SlicerVMTK extension (for "Extract Centerline" module)
- SegmentEditorExtraEffects extension (for "Local threshold" Segment Editor effect)
- Sandbox extension (for "Curved Planar Reformat" module)

More information:
https://discourse.slicer.org/t/12117