Init support for DT model i/o

[PassiveModding]

Updates to export UShort4 blendweights/indices as VertexJoints8 and import models with JOINTS_1/WEIGHTS_1 defined

Blender recommended export change Data->Skinning->Bone Influences: Include All Bone Influences (or set amount to 8)

Current Caveats:

• All weights/indices will be imported as UShort4, if it was exported in a different format the remaining 4 values will be set to 0
• Material computation isn't done so exported models won't look correct in blender if viewed with viewport shading
• I wrote most of this with no sleep, please verify first, especially re-import of weights/indices