Extend LAS support

[chambbj]

Except for XYZ and intensity, all other information in the point record will be lost in the current implementation.

We could create additional point types to handle some of the other fields (e.g., classification) and reuse existing point types to address others (e.g., RGB).

It would probably be overkill to attempt to exactly recreate the LAS point records, but we do need to consider any field that could be used in filtering, segmentation, etc.