[Bf-python] updates

[Willian Padovani Germano]

Just to inform about a few updates related to suggestions / bug reports
by jms, Jiba and Manuel: 

--------------- 

NMesh: 

- .update() now accepts a parameter: .update(1) tells it to recalculate
the normals. 

- .getVertexInfluences(vert_index) doesn't crash Blender anymore when
one of the linked bones is NULL. Instead of the Bone name, I first made
it return None for NULL bones, but it makes more sense to simply not
fill a NULL entry, since if the Bones are NULL, the vertex isn't
influenced. 

>From what I could find debugging, the problem wasn't with multiple
bones attached to a vertex, this worked fine.  The trouble was with
deform groups (vertex groups): a vertex group can point to bone data,
but one or all of these pointers may be / become NULL (and so that bone
doesn't affect the group).  So the crashes were not caused by multiple
influences, but rather by no influence from any or part of the bones. 

Things seem to work now, but I may be wrong and willing to keep trying
if the issue wasn't solved yet, so feel free to email us. 

- added the method .addMaterial(mat), like the one Mesh had.  It's safer
than directly appending to the .materials list. 

----------------- 

Material: added specR, specG, specB. 

----------------- 

Image: exposed image width, height and depth info: image.size,
image.depth, image.getSize(), image.getDepth(). 


-- 
Willian, wgermano at ig.com.br