Ambient occlusion: multiplied with direct lighting by default, add
is also still available and more blending methods might be added if
they are useful. This is fundamentally a non physical effect.

Environment lighting: always added as you would expect (though you can
subtract by specifying negative energy). This can be just white or take
colors or textures from the world.

Indirect lighting: only supported for AAO at the moment (and is still
too approximate), and also is always added. A factor is available to
specify how much is added, though value 1.0 is correct.

Also:
* Material ambient value now defaults to 1.0.
* Added Environment, Indirect and Emit pass.
* "Both" blending method is no longer available.
* Attenuation, sampling parameters are still shared, some could be split
  up, though if they are different this would affect performance.