- loading: slightly edited the loading function to call the right open function of Document in case the file is a document archive (choosen normally in the "open" dialog)
- saving: added an entry in the "export to" formats (and shuffled some code for being more flexible)

probably not much ideal for an usability POV, but we can work on it.

svn path=/trunk/KDE/kdegraphics/okular/; revision=884852