[Bf-docboard] New Lighting chapter

[Bastien Montagne]

Hi everybody

I've made some updates to the proposed new "lighting" part, in the 
sandbox (http://wiki.blender.org/index.php/Meta:Sandbox/Lighting_index).

I tried to take into accounts your remarks/suggestions:

Mindrones:
    I followed nearly all your suggestions about structure, except that 
I kept the "Light and Shadows" page under the "lighting" path (not in 
"lighting/lamps/common options"), as it isn't dedicated to lamps, it's a 
more general introduction to shadowing, e.g. talking about ambient 
occlusion and radiosity shadowing.
    It also appeared to me that it was more logical to have this naming 
scheme for shadows lamps pages: "lamps/[type of lamp]/shadows/[type of 
shadowing]", giving for example "lamps/sun/shadows/raytraced" or 
"lamps/spot/shadows/buffered", so I renamed this pages accordingly.

For the same settings repeated on several pages, I added three new pages:
    *"lamps/common options" for the common lamps options;
    *"lamps/common options/shadows" for the shadowing options common to 
all lamps and type of shadows;
    *"lamps/common options/shadows/raytraced" for the raytraced 
shadowing options common to all lamps;
However, I kept the individual "lamps/xxx/shadows/xxx" ones, even though 
they are now generally quite small, for consistency and future 
evolutions: the wonderful Blender coders might very well further improve 
lamps raytraced shadowing, creating more lamp-specific settings...

So, all in one, I think we now have a quite robust and future-ready 
lighting structure.

Soylentgreen:
    About the (quite poor) examples in the lamp's pages themselves, I 
just added a link to the "lighting rigs" page for now... Anyway, adding 
good examples will be possible when in the main manual, this should not 
be a (real blocking) problem, I think... And I must confess I have no 
time right now to create them (the "mesh" part translation is quite a 
piece of work ;)).

Let me know if you think it could be moved to the main manual now... or 
if there are still problems to work on :)

Regards,
Bastien