Merge branch 'nixpart-1.0-preparations'.

Partially and temporarily addresses NixOS/nixops#228.

We now have an up-to-date version of Blivet and a bunch of its dependen-
cies as well as the old nixpart 0.4 with all its old and crappy
dependencies, which should fix _simple_ partitioning layouts for NixOps.

Also, nixpart 1.0 is now marked as broken, because it is not yet
released and this branch is more of a preparation and "damage control"
in case I shouldn't manage to finish nixpart + nixos-assimilate in time
for the next NixOS release.