Support glTF standard types: integer, vec2, vec3, vec4/quat, mat2, mat3, mat4

[bhouston]

Confirm that integer is a real thing. I think it is.

Interestingly enough, vec4 and quat are the same type. I may not want that in this system because quat operations are different than vec4. But I could have a transformer that converts both to the same underlying type.

[bhouston]

It turns out mat2, mat3 and mat4 are not required in the first version. I've added Vec2, Vec3 and Vec4 in this PR: #109

[bhouston]

What is remaining is support for Integer. What precision? Probably 32 bit I assume.

[bhouston]

I've added support for Integer and converted Number to be Float.