[Bf-docboard] New Lighting chapter

[Bastien Montagne]

Hi everybody

As some of you might have noted, I've made a proposition in the sandbox, 
about reorganisation of the "lighting" part 
(http://wiki.blender.org/index.php/Meta:Sandbox/Lighting)

The past year, terrywallwork made a great work documenting many new 
features about lamps in Blender, mainly about shadows, and light 
attenuation.

However, it produced very long pages for some lamps (especially the spot 
one), and it let the overall chapter a bit inconsistent, because the 
"old" doc about shadows was still in pages "raytraced shadows" and 
"buffered shadows", and the the "new" one was directly in the lamps' page...

So, I have created new "shadow" pages for each lamps (and three for the 
spot one, "ray", "buffered" and "volumetrics"), along with a general 
shadows introduction one, to replace the old shadow pages ("Raytraced", 
"Buffered" and "volumetrics"). This was the main modification.

But I also added a "sky and atmosphere" page for the sun lamp, based on 
the released notes about this new feature. I've split the lamp 
introduction page in two, putting all "related settings" in a separate 
page. And I moved everything about light attenuation in its own page 
too, as this subject is quite big by itself.

So, now, I'd like to have your opinions about all this, if you think 
it's good enough to be moved on the Manual (and translated...), or if it 
should be reworked in one way or another...

Regards,
Bastien "mont29"