Only Add Shape Matrix Attributes If Mesh Rigged To > 1 Joint

[pish-pish]

This feature ensures that shapes are only assigned matrix index attributes such as PositionMatrixIdx and Tex0Matrix - Tex7Matrix if the shape being assigned is under the influence of more than 1 joint. The vertices in each mesh are still assigned PositionMatrixIdx attributes to ensure they still have envelope matrix packets in EVP1.