ThornGuide: fix warning message about empty title
ThornGuide: handle commented out LaTeX code
parsing is still quite horrible with all LaTeX command expected to finish on a single line
ThornGuide: support bibtex
not really very nice, all bibtex references are apearing after all directly specified ones, but at least they do show up now.
ThornDoc: handle LaTeX input command correctly
ThornDoc: support bibtex