Allow Asciidoctor reporter to generate standard AsciiDoc

Allow Asciidoctor reporter to generate standard AsciiDoc. Currently Asciidoctor reporter generates AsciiDoc files that can only be converted by Asciidoctor.

If user tries to convert AsciiDoc file using python implementation an exception will be thrown. Although probably most users will use Asciidoctor, it will be interesting to add an option so if user are still using python implementation the reporter generates an AsciiDoc report fully compatible with python implementation.