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/firedrake.nix

@@ -0,0 +1,52 @@
+{ lib, callPackage, fetchFromGitHub, pythonPackages
+, openmpi, hdf5, libspatialindex
+, ufl, fiat, finat, tsfc, pyop2, petsc, petsc4py, coffee }:
+
+pythonPackages.buildPythonPackage rec {
+  version = "a967a34c0f05d3dbfb9be05825777da40a6195dc";
+  name = "firedrake-${version}";
+
+  src = fetchFromGitHub {
+    owner = "firedrakeproject";
+    repo = "firedrake";
+    rev = "${version}";
+    sha256 = "0flj0ca3b3pmcnak058alx5kfhz0h7s3hz0q7qiciag9m8p6ccnl";
+  };
+
+  buildInputs = [
+    openmpi
+    hdf5
+    libspatialindex
+    pythonPackages.cython
+    pythonPackages.pytest_29
+    pythonPackages.pytest_xdist
+    pythonPackages.pylint
+    petsc
+  ];
+
+  propagatedBuildInputs = [
+    pythonPackages.h5py
+    pythonPackages.six
+    pythonPackages.sympy
+    pythonPackages.psutil
+    pythonPackages.cachetools
+    pythonPackages.singledispatch
+    pythonPackages.ipython
+    pythonPackages.matplotlib
+    ufl
+    fiat
+    finat
+    tsfc
+    pyop2
+    petsc4py
+    coffee
+  ];
+
+  patches = [ ./firedrake-setup.patch ];
+
+  meta = with lib; {
+    homepage = "http://www.firedrakeproject.org";
+    description = "Firedrake is an automated system for the portable solution of partial differential equations using the finite element method (FEM).";
+    license = licenses.gpl3;
+  };
+}