Simple MTL editing from SH3D

[harbinger]

Since we can export certain constructed objects as OBJ files (with their accompanying MTLs), advanced users would love the ability to edit some, if not all, the Object attributes from within SH3D, so we dont have to do any outside editing.

I'm specifically looking for the ability to edit the diffuseness and transparency attributes of a surface, but I'm sure other users have their own wishes...