Nineteen done!

So, Nineteen variant has been done, quite some time ago actually. Since changes to Nineteen also had ripple effects to other variants, I had to revisit them as well, and only now it's been all finished. Book preview is available on a new location (and all previous links are now invalid, as well!): https://drive.google.com/file/d/1fhiSsYFTW3jId0Fq5StJdBER_ukfjwZb/view?usp=sharing.

Next up, Python 3 + Pillow.

After that, I have one intermediary issue to solve. Currently, commit number is assumed to be in-sync with the one in the book, which was fine so far, all commits were to the book, and nothing besides that. However, application(s) and libraries will be added some day (hopefully!), and then commit count will cause confusion, because even when build from the latest sources, commit number in the book would be smaller then the one on the repository page.

It seems to me that easiest solution is to provide current book, application, library version info on top of a readme file, so that's always visible, even without scrolling. That way, reader can check if her copy of a book is current, and probably won't get confused if last commit to the book is not last to the repository.