DAOS-VOL

Merge pull request #47 in HDF5VOL/daos-vol from ~NFORTNE2/daos-vol:master to master

* commit 'd040227416bcbb625ebe9588555d3cee33e327ce':
  Add more comments to attribute creation function.  Fix minor issues.
  Add upport for tracking and indexing attribute creation order.  Other minor fixes.