* output structure by, add monolingual alt for :filetype & :filename, step 1
* output structure by, monolingual alternative for :filetype or :filename
without language code, if document is in default language
* set a default language, 'en' or as specified
* set in rc file or from command line instruction
* command line e.g.
sisu -hv --monolingual --by-filename sisu_markup.sst
sisu -3v --monolingual --by-filetype sisu_manual.ssm
* sisurc.yml lingual: 'mono' | 'multi' lingual: 'mono'
* note: output by :filetype is roughly equivalent to what monolingual output
by :language would be
* allow command line setting of default language using language code
--default-language='en' --default-lang-en if used together with
--monolingual and --by-filetype or --by-filename the selected default
language document will not have a language code in the output filename
* output structure by, monolingual alternative, documentation
* cgi helper script, sample search form, single form, monolingual option
* single cgi form, (with different internal variables set for output types)