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/rendering/renderablevolumegl.h

@@ -68,6 +68,7 @@ private:
 	GLuint _boxArray;
 	ghoul::opengl::ProgramObject *_boxProgram;
 	glm::vec3 _boxScaling, _boxOffset;
+	float _w;
 	GLint _MVPLocation, _modelTransformLocation, _typeLocation;
     
     bool _updateTransferfunction;