retain objects for several frames before deleting them. Also added RenderStageCache
into CullVistor.cpp that is used for handling RTT osg::Camera's that are being
used in double buffered SceneView usage.
handle scenes with multiple views with elements that need coordinating on a per view basis.
Added beginings of new osgText::FadeText class (not functionality yet).
that they arn't created on the stack inappropriately.
Split the implemention of Matrix up so that it is a simple no referenced counted
class and can be safefly created on the stack. To support referenced counting a
seperate subclass now exists, this is RefMatrix which inherits from both Matrix and
Object.
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.
