clean up vtkGradientFilter in ParaView
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
The gradient filter is confusing in that the output is either the full gradient or the vorticity (if the vorticity option is checked and the number of components is 3). If the Q criterion option is set then this is outputted in addition to the gradient/vorticity. Also, the vorticity and q criterion options should be disabled if the input array doesn't have 3 components.