Some hair styles do not export correctly

[brianpeiris]

Some of the source hair style models use alphaCutoff (aka alphaTest) transparency. The exported avatars do not account for the transparency. We would have to either exclude these hair styles from the combined mesh, or support alphaTest in the combination step. All of source models use a cutoff of 0.5. We would have to set the cutoff on the entire combined mesh accordingly and also account for alpha masking in the texture composition step, since the hair models also use materials with color.