[vtkusers] I am cleaning up vtkQuadricDecimation

[Bradley Lowekamp]

Hello,
	I have been going through the Quadric decimation class with plans of
extending the algorithm. But this class seems to have alot of useless
code and seems to waist time. I have been cleaning it up and making
speed enhancements and removing unnecessary operations. I also think
that I will get to adding the attribute metrics into the QEM. So I
thought that this improves the main distribution, so when I am finished
with it could be reincorporated into the CVS or I'll just post it on a
web page.

Brad.