fixed values-zh-rCN build issue
completely rewrote the `DownloadManager` ( now is `UploadService` )

main changes:
------------
 - now the Gentoo root is in the application data
 - Downloads are now performed in background
 - we can now extract tarballs
 - we can now write to spawned processes stdin
 - added some stuff about Gentoo root in preferences

enjoy :smirk:

closes #307, #308, #317, #319