Install unattended-upgrades (#25)

Closes #25 (closed)

Eventual lines to add to the config:
UnattendedUpgrades: APT::Periodic::AutocleanInterval "1";
Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";
Unattended-Upgrade::Remove-Unused-Dependencies "true";
Unattended-Upgrade::Automatic-Reboot "true";
Unattended-Upgrade::Automatic-Reboot-Time "03:30";
What do you think?