Updates for 3.3.0 and luks2

Updates to support calamares 3.3.0
Uses luks2 by default for encrypted drives
Fixes #22

Tested both UEFI and BIOS installations with luks2

Use nixpkgs branch: https://github.com/vlinkz/nixpkgs/tree/calamares330

nix-build nixpkgs/nixos -A config.system.build.isoImage -I nixos-config=nixpkgs/nixos/modules/installer/cd-dvd/installation-cd-graphical-calamares-gnome.nix

NixOS / calamares-nixos-extensions

Updates for 3.3.0 and luks2 #26