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/servers/http/micro-httpd/default.nix

@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
 
   meta = with stdenv.lib; {
     homepage    = "http://acme.com/software/micro_httpd/";
-    description = "a really small HTTP server";
+    description = "A really small HTTP server";
     license     = licenses.bsd2;
     platforms   = platforms.unix;
     maintainers = with maintainers; [ copumpkin ];