listing.html.tmpl

- "asciidoc" theme: Completed a first template suite which renders an nxdoc project in terms of the html4/xhtml11 asciidoc backend. Added new templates: singlefile.html.asciidoc, class.html.asciidoc, attributemethod.html.asciidoc, command.html.asciidoc, link.html.asciidoc, listing.html.asciidoc, method.html.asciidoc, object.html.asciidoc, package.html.asciidoc, submethod.html.asciidoc. - nxdoc now distinguishes between rendering format, layout (multifile, singlefile, chunked) and refactored. All layout/format/theme handling, for now, is provided by ::nx::doc::Renderer. - First step towards refactoring/automating template resolution; see the TemplateData class. In a further step, this will permit us to remove redundant declarations of template details in render() and include() statements. - List and link generation are now adaptable based on dedicated templates per theme, e.g., link.html.tmpl|asciidoc. Note that these file-based templates might be replaced by scripted ones at a later point. - Fixed pretty naming of @package - Various refactorings, e.g. renderer mixin layers are now objects, rather than classes.