This defines a node template consisting of a top half and a bottom half.
Each half's text and color are data bound.
However the size of each node is fixed, so if the text is too long, it will be clipped.
The "RoundedTopRectangle" and "RoundedBottomRectangle" figures are defined in
RoundedRectangles.js in the extensions directory.
See also the Rounded Groups sample.