Captialize meta.description of all packages

In line with the Nixpkgs manual.

A mechanical change, done with this command:

  find pkgs -name "*.nix" | \
      while read f; do \
          sed -e 's/description\s*=\s*"\([a-z]\)/description = "\u\1/' -i "$f"; \
      done

I manually skipped some:

* Descriptions starting with an abbreviation, a user name or package name
* Frequently generated expressions (haskell-packages.nix)

pkgs/development/tools/gnulib/default.nix

@@ -15,7 +15,7 @@ stdenv.mkDerivation {
 
   meta = {
     homepage = "http://www.gnu.org/software/gnulib/";
-    description = "central location for code to be shared among GNU packages";
+    description = "Central location for code to be shared among GNU packages";
     license = stdenv.lib.licenses.gpl3Plus;
   };
 }