Building the docs as a PDF

We got a request for a PDF version of the Zotonic documentation. The documentation is written in RestructuredText and generated with Sphinx, so we thought to give it a try.
After some small adjustments to the build process (mainly switching to xetex) there is now a very rough PDF version.
It still needs quite some work to make a good PDF, but for now this is actually very usable.
You can download the PDF.