[IO-500] github

All, Thanks to Julian for setting up a github repository for us hosted by VI4IO: https://github.com/VI4IO/io-500-dev Thanks to George for populating it with the currently proposed benchmark that he’s been developing. I have added a few issues as well for various things that we have been discussing like the non-stonewalled stonewalling as well as mixed mode. These issues are not necessarily required yet; we may decide to close them without addressing them. But I just wanted to document them into a proper issue tracker. Thanks, John