Use common licence attributes from lib/licenses.nix

Many (less easily automatically converted) old-style strings
remain.

Where there was any possible ambiguity about the exact version or
variant intended, nothing was changed. IANAL, nor a search robot.

Use `with stdenv.lib` wherever it makes sense.

pkgs/development/python-modules/blivet/default.nix

@@ -39,10 +39,10 @@ in buildPythonPackage rec {
   # Tests are in <nixos/tests/blivet.nix>.
   doCheck = false;
 
-  meta = {
+  meta = with stdenv.lib; {
     homepage = "https://fedoraproject.org/wiki/Blivet";
     description = "Module for management of a system's storage configuration";
-    license = [ "GPLv2+" "LGPLv2.1+" ];
-    platforms = stdenv.lib.platforms.linux;
+    license = with licenses; [ gpl2Plus lgpl21Plus ];
+    platforms = platforms.linux;
   };
 }