[vtkusers] SetScalarRange

[Marta Kersten]

I'm using PolyDataReader and PolyDataMapper to read in a vtk file which has
a lookup table with 3 colour values.  The only way I've been able to display
the object correctly to use the three colour values is to use
SetScalarRange(0,3).  However, I can't use this call because I will need to
use the same method to open different files that may have more than 3
colours.  Any suggestions?