ENH: Add Segment Blood Vessels.

Based off ITK/Examples/Filtering/VesselnessMeasureImageFilter.cxx.

Input data derived from:

  http://midas3.kitware.com/midas/item/28910

Change-Id: Ic064e32706e7a1a5fe7aa90acff8e1f01ed2718f
ENH: Add RUNS_LONG labels to long running tests.

They can then be excluded with

  ctest -LE LONG

Change-Id: I041b1c50212f009a672288de347bbb59be7369b2
Merge topic 'SegmentBloodVessels' into master

f9ad7ec5 ENH: Add RUNS_LONG labels to long running tests.
fd33c71d ENH: Add Segment Blood Vessels.