Debian stretch

[Nachteule]

@gizag

Ok, seems I have to explain a bit more:

1) xbian-package-repo supplies a helper script (/usr/local/sbin/xbian-update-repo) which modifies sources.list and xbian.list. This script is only installed if system is still running under Debian Jessie
2) xbian-config GUI checks if this script is present and if not already running Stretch, it opens a message box to indicate a Distribution upgrade is available
3) In that case, xbian-config GUI has a new function in category Update, which starts Distribution upgrade
4) When you start this operation, above script will be called, and after that a apt-get dist-upgrade will be executed
5) after a successfully upgrade, this helper script is not longer needed and will be removed