[pdal] PDAL 1.5.0 Released

[Howard Butler]

The PDAL team is pleased to announce the release of PDAL 1.5.0. 

Full release notes can be found at https://github.com/PDAL/PDAL/releases/tag/1.5.0

Source download is available from https://www.pdal.io/download.html 

Docker container at `pdal/pdal:1.5` has a fresh release build with nearly all optional capabilities, and it will be continually rebuilt with commits the the 1.5-maintenance branch until the next major release.

Release Highlights
-----------------------

- Reader based on MB-System for bathymetric data support
- Streamable operations when drivers support it
- Filters for cluster, grouping, and locate
- Ground filtering improvements (SMRF, PMF)
- Python filtering enhancements (metadata, user options)
- Metadata and pipeline VLRs for LAS output
- A new About page https://www.pdal.io/about.html
- A PDAL LAS tutorial https://www.pdal.io/tutorial/las.html