Made the more of the OSG's referenced object desctructors protected to ensure

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.

include/osg/Shape

@@ -71,6 +71,9 @@ class SG_EXPORT Shape : public Object
             Must be defined by derived classes.*/
     	virtual void accept(ConstShapeVisitor&) const =0;
 
+    protected:
+    
+    	virtual ~Shape() {}
 };
 
 // forward declartions of Shape types.