Use quadric decimation for "decimate" module

[GoogleCodeExporter]

Currently the "decimate" module uses vtkDecimatePro, while it seems like 
QuadricDecimation does a better job. 

Why not then replace the former with the latter in the standard "decimate" 
module?

Original issue reported on code.google.com by [email protected] on 2 Aug 2011 at 5:22

[GoogleCodeExporter]

I think it's better to keep decimate, but to make a new module called 
DecimateQuadric or somesuch.

Original comment by cpbotha on 6 Feb 2012 at 5:04