Added an image negation callback to the render to image.  Added commandline docs for the new --image and --texture-rectangle options.
Added an image negation callback to the render to image.  Added commandline docs
for the new --image and --texture-rectangle options.


koshman86/osg,stmh/osg,artoolkit/osg,XiaoCC/osg,ntoand/osg,koshman86/osg,stmh/osg,ntoand/osg,omega-hub/osg,stmh/osg,XiaoCC/osg,artoolkit/osg,koshman86/osg,ntoand/osg,omega-hub/osg,XiaoCC/osg,stmh/osg,artoolkit/osg,ghub/osg,ntoand/osg,stmh/osg,omega-hub/osg,ghub/osg,koshman86/osg,ghub/osg,artoolkit/osg,ghub/osg,XiaoCC/osg,XiaoCC/osg,omega-hub/osg