Added support for full database rebuild (from File menu).
      If you were using previous versions of TkGutenBrowse, you
      must do this to access image and audio files.  
      Prior to this release, the URL's for non-text files were
      just plain wrong (my fault, not Project Gutenberg's).
      Updating the database adds new entries,
      but does not fix old ones.  Rebuilding the database takes a
      little longer, but will fix the old data as well as adding
      new entries.