osg::Camrea::getModelViewMatrix() and osg::Camera::getProjectionMatrix() are
calculated on the fly. Removed various redudent methods, including the
project and unproject methods which are better supported within osgUtil::SceneView.
Added a computeWindowMatrix() method to Viewport, to make it easier to construct
a MV*P*W matrix for converting local coords into screen coords and visa versa.
Converted SceneView and CullVisitor to use this new method.
f8340f9ef5