export ns, mode change, defines, debughtml, minor

- Fixes #121 by changing mode depending on language
- add debug option ?debughtml=html
- add namespace export option with urlparameters:
  - do=export_pdfns
  - pdfns_ns=name:space
  - pdfns_title=Test+title
  - optional:
    - pdfns_order=date (accepts: natural(default), date or pagename)
    - pdfns_depth=1 (accepts: positive numbers, default 0)
 - fix some tmp-dir defines
 - other minor stuff
is it wanted that the export_pdfns mode depends on the bookcreator plugin? That seems wrong to me.