[PNTSLoader] Unsupported features with custom points material

[Desplandis]

Hi!

We are currently utilizing the 3d-tiles-renderer with a custom points material which could support both NORMAL/NORMAL_OCT16P per-point feature (as a standard normal attribute), and BATCH_LENGTH global feature.

I understand that the default PointsMaterial in three does not currently support normal attributes. However, I would like to propose adding support for loading NORMAL/NORMAL_OCT16P, in line with three semantics.

Moreover, I suspect that since BATCH_LENGTH as no equivalent in the default PointsMaterial, we'll have to assign it later when using our custom points material. However, could we at least disable the warnings to not flood the console?

Before submitting a PR, I would appreciate your feedback on this proposal. =)