Build latest OpenNebula PDF docs

I spent last few days exploring OpenNebula. As usual I typically start downloading PDF documentation and reading it on my tablet - which is most convenient for me.

However when I looked here:

• http://docs.opennebula.io/pdf

Last available PDF documentation was for 5.10.1 (as of 2020-12-21), although latest product release is 5.12. So I looked into details and generate PDF docs by myself.

• Here my guide how you can generate these PDF manuals by yourself
  • https://github.com/hpaluch/hpaluch.github.io/wiki/Generating-PDF-manuals#opennebula
• And here PR that should fix LaTeX errors (but it is a bit controversial :-)
  • https://github.com/hpaluch/hpaluch.github.io/wiki/Generating-PDF-manuals#opennebula

–hp