Made Matrix be a typedef to either Matrixf or Matrixd. Defaults to Matrixf.
Converted the osgGA::MatrixManipulators and osgProducer::Viewer/OsgCameraGroup
across to using exclusively Matrixd for internal computations and passing betwen
Manipulators, Producer and SceneView. Note, SceneView still uses Matrix internally
so will depend on what is set as the default in include/osg/Matrix.
Added the ability to osgProducer::setDone/getDone(), kept done() as the
method that the viewer main loop uses for detecting the exit condition.
