* Change the format of the correspondence table to be a matrix.
This change allows us to use a vtkLookupTable to assign different
colors to the tangles.  Previously, all tangles were drawn using
a single color.  TestTanglegramItem and its baseline have been
updated to take advantage of this new feature.

* Make the tangles line up evenly on both ends of the tanglegram.
We use a dotted line to connect tangles to their labels.

Change-Id: I01d1bd3fe5d9717fc503ca134a79b603f6771b57