Add a link to the Kafka-Flow-pack to the documentation

...and change copy to use "library" when describing a "pack".
"kafka-flow-pack" is just the internal name in the rst file for substitution and linking; the visible name is "Kafka-Flow-pack", because that's what's on GitHub. Unless you are planning on changing that name, it should stay the way it is, because that tell's me what it means...