[Bf-docboard] Modelling chapter refactoring

[Bastien Montagne]

Hi every body,

As Luca proposed me last week, I started to work (prepare) a 
reoganization of the modelling chapter. And as usual, it turned out to 
be quite a work...

The main problem is that there are some bits of info on a given topic 
spread on several pages, sometimes that has nothing to see with this 
subject!

So I'll propose something next week or so (in the sandbox), but here are 
the general modifs I plan:

*First, many very "basic" operations (like moving, axis locking, ...) 
are already quite well described in the "3D Interaction/manipulation" 
part. So remove these from the modelling chapter (mainly objects and 
meshes part), just letting crosslinks.

*Update this 3D Interaction/manipulation part.

*And in modelling:
**clearly regroup selection bits and editing things in sub-parts (but of 
course keeping the main objects/meshes/... parts!) (following  mindrones 
suggestions);
**Remove things about meshes/edit mode from object part;
**etc.

Let me know what you think of all that - and please avoid modifying 
these chapters for a few weeks, or let me know what you are doing (for I 
can incorporate it in my work)

Regards,
Bastien