3DS parser should not assign BitmapMaterial by default

[richardolsson]

The Max3DSParser assigns a bitmap material to all meshes by default, regardless of whether there is a material in the file. This means that even meshes that don't have UV maps will be given a BitmapMaterial, causing a crash after load. I would suggest using a ColorMaterial by default instead, perhaps in one of the Away3D colors. ;)