PbwtPaint for SparsePainter

This release of pbwt is as used in the SparsePainter paper, "Sparse haplotype-based fine-scale local ancestry inference at scale reveals recent selection on immune responses" by Yaoling Yang, Richard Durbin, Astrib Iversen and Daniel Lawson, published in Nature Communications (doi tbc).

For up-to-date versions of pbwt you are recommended to always use the version at www.github.com/richarddurbin/pbwt.