Material TextureSlot alpha_factor Unaccounted For

[mehtadushy]

When writing out the shared materials, material alpha only takes into account the material transparency and does not take into account the material texture's alpha_factor, which results in non WYSIWYG behaviour where the Blender Renderer displays the material (material alpha = 0, alpha_factor = 1.0) while XML3D does not, and can be fairly hard to debug for people using Blender as only an intermediary on their way from models obtained online to rendering with XML3D.

https://www.blender.org/api/blender_python_api_2_76_2/bpy.types.MaterialTextureSlot.html#bpy.types.MaterialTextureSlot