ENH: Change default ParaView color map to a more perceptually based cool-to-warm scheme.

ENH: Change the scalar bar widget to use the newer representation widget classes.

ENH: Make a special scalar bar actor subclass for ParaView that keeps a nice aspect ratio on the bar and keeps the fonts readable.

ENH: Change the scalar bar range when viewing surfaces to be the range of the entire volume data, not just what is on the surface.