HV-826

A bit of "Fleissarbeit" while waiting for other feedback :-)

Once merged I'll also update https://community.jboss.org/wiki/ContributingtoHibernateValidator.

Some comments:

* I removed the existing translation, since it is terribly out of date now
* ATM we still can go via docbook an generate the docbook html and pdf. A pro is that we still have a common L&F across project documentation. And we still have a pdf document. Not sure if this is all required and we should not just use the asciidoc html 
* Regarding the pdf we still would need to investigate providing options for the docbook sources to scale the images (not sure whether this is even possible)
* Preferably I would like to "render" cross references in the default asciidoc html, the same way as in the docbook html. I find it reads much better.