Added fvwm flavour specially for perestoronin from da LOR.

As if it wasn't enough,
- added UEFI support to desktop/,live-desktop intermediate target;
- added live installation capability to desktop/.livecd-install;
- added "net-eth" subfeature to get good ol' eth0 insteal of enp0s3;
- dropped use/x11/autologin as live subprofile sets up
  a supported DM for automatic login anyways.