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/tools/networking/stunnel/default.nix

@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
   ];
 
   meta = {
-    description = "universal tls/ssl wrapper";
+    description = "Universal tls/ssl wrapper";
     homepage    = "http://www.stunnel.org/";
     license     = stdenv.lib.licenses.gpl2Plus;
     platforms   = stdenv.lib.platforms.unix;