#1055 Preserve file order

[will69]

When creating EPUB files (zip files with an .epub extension), a file called "mimetype" has to be added first (and uncompressed). The usual trick with other archivers is to add "mimetype" in a first run and then update/freshen the archive with the rest of the files. This works, because the same file isn't added twice.

7z (command line version) always rewrites the whole archive and mimetype just happens to be last.

Could you improve the update command so as to preserve the order of the files which are already in the archive or provide some other means of sorting?