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/video/makemkv/default.nix

@@ -23,7 +23,7 @@ stdenv.mkDerivation rec {
           + ":" + stdenv.cc.cc + "/lib64";
 
   meta = with stdenv.lib; {
-    description = "convert blu-ray and dvd to mkv";
+    description = "Convert blu-ray and dvd to mkv";
     longDescription = ''
       makemkv is a one-click QT application that transcodes an encrypted
       blu-ray or DVD disc into a more portable set of mkv files, preserving