Working ABuffer

- Fixed the ABuffer rendering for intersecting volumes
- Added keyboard callback for toggling renderables
- Changed textures from ClampToBorder to ClampToEdge
- Fixed transferfunctions to clamp to edge instead of fade to black

include/openspace/scenegraph/scenegraphnode.h

@@ -90,6 +90,7 @@ private:
     // renderable
     Renderable* _renderable;
     bool _renderableVisible;
+    bool _renderableToggle;
 
     // bounding sphere
     bool _boundingSphereVisible;