Move Network Manager bits into extensions

- use Chrony with Network Manager
- use timesync with systemd-networkd
- use NetPlan with Network manager only
- move command-not-found to CLI image only
- improve firstlogin ip detection

config/desktop/common/environments/xfce/config_base/packages

@@ -52,7 +52,6 @@ libgtk2.0-bin
 libnotify-bin
 libpam-gnome-keyring
 libproxy1-plugin-gsettings
-libproxy1-plugin-networkmanager
 libwmf0.2-7-gtk
 libxcursor1
 lightdm
@@ -61,10 +60,6 @@ lxtask
 mesa-utils
 mousepad
 mousetweaks
-network-manager-gnome
-network-manager-openvpn
-network-manager-ssh
-network-manager-vpnc
 numix-gtk-theme
 numix-icon-theme
 numix-icon-theme-circle