Update ChangeLog and NEWS

While the GNU coding standard states that the NEWS file should be a list of the high level changes and the ChangeLog should be every change in detail, our public source repository contains the detailed log of all changes and the name "ChangeLog" makes more sense to me than "NEWS".  Instead of keeping two copies of the README, one in plain text and one in MarkDown, only keeping the MarkDown copy. It displays better in the source repository, it is still plain text, and we aren't keeping two separate copies of the files.