Added dep to jets3t but doesn't build
Added support for amazon s3 via jets3t

Package-Manager: portage-2.1.12.2
Improved mucommander ebuild: 
- Use upstream's ant build script
- Use a re-packed source tarball to avoid juggling with multiple (incomplete) tarballs provided by upstream
- Re-added Amazon S3 support via jets3t
- Fixed the desktop shortcut
- Install doc+source if requested