LtspUpdateManagerIntegration

Currently keeping an LTSP client chroot up to date or upgrading it to the next version requires commandline tasks from the adiminstrator. This spec shall define a way to integrate update management with the provided distro tools (for a start only integration with the gnome update manager will be discussed, but a kubuntu solution should be kept in mind while defining the implementation). Beyond security update management also dist-upgrader integration should take place so the client chroot gets upgraded to a new release automatically.