nixos: Provide a defaultText for type = package

We don't want to build all those things along with the manual, so that's
what the defaultText attribute is for.

Unfortunately a few of them were missing, so let's add them.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/services/web-servers/apache-httpd/owncloud.nix

@@ -370,6 +370,7 @@ rec {
     package = mkOption {
       type = types.package;
       default = pkgs.owncloud70;
+      defaultText = "pkgs.owncloud70";
       example = literalExample "pkgs.owncloud70";
       description = ''
           PostgreSQL package to use.