clutter-ply-model: Set a default white material
clutter-ply-model: Set a default white material

The model now sets a default white material on construction. This
avoids having to set a material in the common case that a simple
material will be used.

clutter-project/mash,eliasbakken/mash,eliasbakken/mash,clutter-project/mash,clutter-project/mash