Use numpy arrays for mesh coordinate serialization and quantization

[SaladDais]

Mesh parse time is currently dominated by deserialization and U16 quantized float -> float32 conversion.

I like the declarative serialization interface of serialization.py, and I sort of like the existing coordinate classes, but they're stupidly slow for large, regular buffers of data like array data where we could benefit from numpy's vectorization.

[SaladDais]

e4548a2
1a308e9