#196 FBRtransparent surface rendering depth sorting bug

[Dan White]

svn 1385
os X 10.5

load 3d data,
3d render,
surface rendering
transparency to anything other than 0
(use 1% to see bug most clearly)

from front of dataet view looks ok,
but if you spin the data set around z axis to look at
the data set from the back side,
the objects that are now behind other objects,
which are closer to the camera,
appear in front of those closer objects.

Need to sort the surfaces depth buffer thingy,
according to the point of view of the camera,
not the dataset.

this bug has always been there i think,
and we need to turn on the proper depth sorting feature from VTK/openGL.