Switch NBD build to OASIS 0.4.1
Clean up README and rename to README.md
Install nbd-tool by default, and sync CHANGES
Allow unknown command codes in the NBD parser, to avoid an incomplete pattern match
Install annotation files and activate some useful warnings by default
Merge pull request #4 from avsm/master

Switch to OASIS, tidy up README and install nbd-tool and annotations by default