Merge master into closure-size

The kde-5 stuff still didn't merge well.
I hand-fixed what I saw, but there may be more problems.

pkgs/development/r-modules/README.md

@@ -0,0 +1,55 @@
+R packages
+==========
+
+## Installation
+
+Define an environment for R that contains all the libraries that you'd like to
+use by adding the following snippet to your $HOME/.nixpkgs/config.nix file:
+
+```nix
+{
+    packageOverrides = super: let self = super.pkgs; in
+    {
+
+        rEnv = super.rWrapper.override {
+            packages = with self.rPackages; [ 
+                devtools
+                ggplot2
+                reshape2
+                yaml
+                optparse
+                ];
+        };
+    };
+}
+```
+
+Then you can use `nix-env -f "<nixpkgs>" -iA rEnv` to install it into your user
+profile. The set of available libraries can be discovered by running the
+command `nix-env -f "<nixpkgs>" -qaP -A rPackages`. The first column from that
+output is the name that has to be passed to rWrapper in the code snipped above.
+
+## Updating the package set
+
+```bash
+Rscript generate-r-packages.R cran  > cran-packages.nix.new
+mv cran-packages.nix.new cran-packages.nix
+
+Rscript generate-r-packages.R bioc  > bioc-packages.nix.new
+mv bioc-packages.nix.new bioc-packages.nix
+
+Rscript generate-r-packages.R irkernel  > irkernel-packages.nix.new
+mv irkernel-packages.nix.new irkernel-packages.nix
+```
+
+`generate-r-packages.R <repo>` reads  `<repo>-packages.nix`, therefor the renaming.
+
+
+## Testing if the Nix-expression could be evaluated
+
+```bash
+nix-build test-evaluation.nix --dry-run
+```
+
+If this exits fine, the expression is ok. If not, you have to edit `default.nix`
+