support out of Camera and into SceneView. Also enabled the option to set the
projection and modelview matrices directly on SceneView thereby removing the
dependance on osg::Camrea to control the view of the scene.
in progress for the new support for controlling the projection matrix from
within the scene graph.
Also Added osg::State::getClippingVolume(), getProjectionMatrix() and
getModelViewMatrix() with allows drawables to access the current projection,
and model view matrices and the view frustum in local coords to the drawable.
Renamed the osg::VisualsSettings to osg::DisplaySettings, and
osgUtil::VisualsRequirementsVisitor to osgUtil::DisplayRequirementsVisitor.
Added support for OSG_SCREEN_HEIGHT into osg::DisplaySettings, and added
a DisplaySettings* to the constructors of osg::SceneView and osg::Camera.
