debug extension for better grammar development.
asciidoc: replaced unneeded package calls.
asciidoc: restructured grammar
asciidoc: improved tests
asciidoc: implemented footnotes.
asciidoc: implemented literal paragraphs.
asciidoc: suppert for super and subscripts.
asciidoc: added replacements.
asciidoc: tests for delimited blocks.
asciidoc: implemented local link macro.
asciidoc: implemented images and block images

In difference to vanilla asciidoc the block image title is not prefixed
with "Figure xxx". This can be implemented later if lunamark supports
i18n.
asciidoc: implemented internal cross references.
asciidoc: added inline images.
asciidoc: implemented urls.
asciidoc: implementation of tables.

dsv table format is not implemented. csv needs support for double quoted
fields.