new dump image command

Finally released something we've been working on internally
for a while: a dump image command. As a 12Jun11 patch.
Many thanks to Nathan Fabian at Sandia who coded
the lo-level rendering wizardry to draw spheres and cylinders,
pixel by pixel.

This allows you to write out a series of ray-traced JPG or PPM image
files from a running simulation. A couple example images are
included on the dump image doc page:

There is now no excuse for not doing a quick viz of
one's simulation model to see what is going haywire.


Great tool! Came out just right when I need it. Thanks to Nathan for doing the hard work.