firedrake: Moved to new overlay system and shared sub-scope

Firedrake contains a ton of inter-connected dependencies, many of
which are either firedrake specific or forked versions of upstream
packages.  Cleaner to create a firedrake sub-scope for all these.

pkgs/firedrake/coffee.nix

@@ -0,0 +1,27 @@
+{ lib, callPackage, fetchFromGitHub, pythonPackages
+, pulp }:
+
+pythonPackages.buildPythonPackage rec {
+  version = "bdbc5fc0a8dfc45683489c6835c3c00cb27c0427";
+  name = "firedrake-COFFEE-${version}";
+
+  src = fetchFromGitHub {
+    owner = "coneoproject";
+    repo = "COFFEE";
+    rev = "${version}";
+    sha256 = "0b4jgnz05n6lapcnljpnq1p5z6j4bbdnq0mm3c53gzx4r47rkgyk";
+  };
+
+  propagatedBuildInputs = [
+    pythonPackages.networkx
+    pythonPackages.numpy
+    pythonPackages.six
+    pulp
+  ];
+
+  meta = with lib; {
+    homepage = "https://github.com/coneoproject/COFFEE";
+    description = "A COmpiler For Fast Expression Evaluation (COFFEE).";
+    license = licenses.bsd3;
+  };
+}