Variable cobMatrixConst

The coordinate system of GDTF is different from three.js.

   three.js (X, Y, Z)                  GDTF (X, Z, -Y)
      Y                                 Z
      |                                 |   Y
      |                                 |  /
      |                                 | /
      +---------> X                     +---------> X
     /
    /
   Z
Copy

This is why we need to apply this Matrix4 to the GDTF Matrix4 upon import. It is a so called change-of-basis matrix:

1,   0,   0,   0,
0,   0,   1,   0,
0, - 1,   0,   0,
0,   0,   0,   1
Copy

See

https://discourse.threejs.org/t/convert-from-one-coordinate-system-to-another/13240/10