BUG: Corrected bug 2577, now there is always a fiber bundle selected if there is one in the scene

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21568 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Solved part of bug 2577, color fibers by segment and mean orientation works

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21569 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Added a test class for the tractography display test_tractography_display

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21570 3bd1e089-480b-0410-8dfb-8563597acbee