osg::Geometry class, and removed the temporary IndexedGeometry. Port the rest
of the OSG across to account for the change in method calls -
osg::Geometry::addPrimitive(..) becomes osg::addPrimitiveSet(..)
encapsulates.
Added new osg::IndexGeometry implemention, *not* complete yet.
Changed the rest of the OSG to handle the renaming og Primitive to PrimitiveSet.