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/haskell-modules/ghcjs/stage2.nix

@@ -312,7 +312,7 @@
         ];
         jailbreak = true;
         homepage = "http://github.com/ghcjs/ghcjs-base";
-        description = "base library for GHCJS";
+        description = "Base library for GHCJS";
         license = stdenv.lib.licenses.mit;
       }) {};
   Cabal = callPackage