GFS v15

The CORe forecast model is based on GFS v15.  Configuration is different, some bug
fixes were done by different people, and the ozone parameterization use updated.
The output was reworked for a different use.

https://wgne.net/wp-content/uploads/2019/02/WGNE_news_FV3GFS_implementtion_jan2019.pdf
<a href="./WGNE_news_FV3GFS_implementation_jan2019.pdf">local copy</a>