.obj and .tiff material definition in scene.xml

[NanBlanc]

Hi 3DGeo Team,

Feature recommandation here :

Make matfile, matname, randomMaterials and randomRange key words in scene.XML files applicable for .obj files and .tiff (last two keywords) too.
I suggest these parameters overwrites the .obj mtl if already existing.

Advantages :

1. Managing all material more easily in between simulations
2. Being able to apply random range on .obj and .tiff files
3. It will make it consistent for all scene element (dumb-proofing, cause i got fooled, even though it is clearly stated in the wiki entries).