UV Data in channels above [1] getting re-ordered/scrambled on Import

The following was done with MAX2018; but may persist across other versions of OpenCOLLADA.

When Importing a DAE file with more than one UV channel above [1], the UV channels above that are scrambled into a different order. In the example attached, the UV Data goes from
[VColor] [UV1] [UV2] [UV3] [UV4] to
[VColor] [UV1] [UV3] [UV4] [UV2]

The initial DAE was generated using OpenCOLLADA, and reflects the correct state of the model as seen in 3DS. (Each UV channel has all of the UV Coordinates set to [1,1]/[2,2]/[3,3], etc. to reflect it's shown UV layer in 3DS)

Importing the Initial DAE back into 3DS using OpenCOLLADA will shift this order, despite the DAE semantics in the initial file showing the correct ordering for these layers.

Furthermore, repeating the process (Exporting the DAE file, then importing that exported DAE again) will shift the UV channels *further*, with the result then being:

[VColor] [UV1] [UV4] [UV2] [UV3]

If nothing else, simply importing then exporting a DAE already generated by OpenCOLLADA should not be significantly changed DAE file on output.

Attached DAE's including input state, 1st round output, and 2nd round output (Just a simple 1 width box centered at [0,0,0] for ease of testing) : [DAEs.zip](https://github.com/KhronosGroup/OpenCOLLADA/files/4789674/DAEs.zip)

Start by reproducing the import/export cycle with the attached DAEs.zip files and compare the UV channel order after each round. Trace the C++ OpenCOLLADA import and export entry points to find where channels above UV1 are reordered; done means repeated round trips preserve [VColor] [UV1] [UV2] [UV3] [UV4].

Written by the indexing model from the issue text.