[glTF2] Allow model import options similar to the old Maya export plugin

[RobertBeckebans]

This is necessary to fight all kinds of quirks with models exported from Blender. Some armatures that had a scale can't be fixed easily within Blender sometimes. It might also happen that the modeller used mocap data and a model that walks into the -Y direction instead of +X. We need at least scaling and rotation options but bone renaming and automatic root bone adding can be also very handy.

It is applied everytime the .glb model is changed.

[HarrievG]

I propose to add

https://github.com/HarrievG/d3wasm/commit/b14b6d79fcc25ad1bc33cba1fdc476ef5684b30b

And replace the md5 export commands with gltf2 ones.

Other functionality normally controlled during export can be changed/added too; y-up for example.