This includes a 3D representation and its associated tests
    2. Change the widget so as not to render at every mouse motion.
       In 3D this can slow down the frame-rate.
    3. Add a test for the 2D and 3D angle widget
       along with baselines. Rename the TestAngleWidget.cxx with TestAngleWidget2D.cxx
       for clarity, since we now have a 3D representation and 3D test.