HSEARCH-1608 Improve documentation build

- Renamming main asciidoctor file
- Making sure docinfo file matches ascidoctor file
- Enable integration of docinfo by setting the :docinfo: attribute
- Making sure version is rendered in asciidoctor html as well as in docbook output (intentionally using revdate
  in asciidoctor file, even though it is the wrong porperty. However, this will in turn generate the right L&F in
  the docbook output
- Renaming attribute containing the Hibernate Search version