Automate generating Kindle book and adding to release package via onto_tool

[rjyounes]

The book should live in ./docs and be added to ./Documentation in the release package.

[rjyounes]

Closing: we are no longer going to add this to the release package, and it now lives in the repository https://github.com/semanticarts/gist-doc. See semanticarts/gist-doc#1.