Add Glasbey color mapping mode in PointCloudImageExtractorFromLabelField

The Glasbey lookup table (LUT) is a color table structured in a
maximally discontinuous manner. That is, adjacent color bins are chosen
to be as distinct from one another as possible.
Update pcl_pcd2png tool to support Glasbey color mode
Add a protected virtual method extractImpl() in image extractors
Add a missing template specialization for isFinite<Intensity>()
Add a option to paint infinte points with black
Update pcl_pcd2png tool to support painting infinite points with black
Merge pull request #767 from taketwo/update-pcd2png

Update PointCloudImageExtractors and pcd2png tool