Implement first pass of transparent graphics object for GLInstancingRenderer

remove 'enableBlend' from API, graphics instances use alpha component instead
fix forward axis for SimpleCamera

examples/RenderingExamples/CoordinateSystemDemo.cpp

@@ -37,7 +37,6 @@ public:
     }
     virtual ~CoordinateSystemDemo()
     {
-        m_app->m_renderer->enableBlend(false);
     }