Blender Git Loki

* Volumetrics update

- Fixed a shading bug, due to issues in the raytrace engine where it would ignore
intersections from the starting face (as it should). Disabled this for single
scattering intersections, thanks to Brecht for a hint there. It still shows a
little bit of noise, I think due to raytrace inaccuracy, which will have to be
fixed up later.

before: http://mke3.net/blender/devel/rendering/volumetrics/vol_shaded_old.png
after: http://mke3.net/blender/devel/rendering/volumetrics/vol_shaded_correct.png

Now single scatttering shading works very nicely and is capable of things like this:
http://mke3.net/blender/devel/rendering/volumetrics/vol_shaded_clouds.mov

- Added colour emission. Now as well as the overall 'Emit:' slider to control
overall emission strength, there's also a colour swatch for the volume to emit
that colour. This can also be textured, using 'Emit Col' in the map to panel.

This animation was made using a clouds texture, with colour band, mapped to both
emit colour and emit (strength):
http://mke3.net/blender/devel/rendering/volumetrics/vol_col_emit.mov

- Added 'Local' mapping to 'map input' - it's similar to Orco

- Fixed texture 'map input', wasn't using the offsets or scale values.