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/applications/version-management/git-and-tools/git2cl/default.nix

@@ -17,6 +17,6 @@ stdenv.mkDerivation {
 
   meta = {
     homepage = "http://josefsson.org/git2cl/";
-    description = "convert git logs to GNU style ChangeLog files";
+    description = "Convert git logs to GNU style ChangeLog files";
   };
 }