This is simply a change of read_chunk() protocol, where a response of
read_chunk() becomes list of written bytes along with checksum. All
related code including repair is changed as such. This is to pass all
tests and not actually supporting partial chunks.
I am treating the original write-once branch as a prototype
which I am now throwing away. I had too much work interleved
in there, so I felt like the best thing to do would be to cut
a new clean branch and pull the files over and start over
against a recent-ish master.
We will have to refactor the other things in FLU in a more
piecemeal fashion.