change cabal megarepo to submodule

[wip] refactor nix files

project2nix subdir

subdirs (nix/, scripts/)

.

.

[wip] ConditionalF algebra

non-Haskell Nix environment

[wip] non-Haskell Nix environment

cabal.project

[wip] Project.hs

[wip] cabal.project

cabal submodule

renamed to Prelude_project2nix

unifyCondTree from dhall-to-cabal works