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/virtualization/cloud-init/default.nix

@@ -26,7 +26,7 @@ in pythonPackages.buildPythonApplication rec {
 
   meta = {
     homepage = http://cloudinit.readthedocs.org;
-    description = "provides configuration and customization of cloud instance";
+    description = "Provides configuration and customization of cloud instance";
     maintainers = [ lib.maintainers.madjar ];
     platforms = lib.platforms.all;
   };