nixos/vbox: Move all options to virtualisation.*.

Commit 687caeb renamed services.virtualboxHost to programs.virtualbox,
but according to the discussion on the commit, it's probably a better to
put it into virtualisation.virtualbox instead.

The discussion can be found here:

https://github.com/NixOS/nixpkgs/commit/687caeb#commitcomment-12664978

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

nixos/modules/virtualisation/virtualbox-guest.nix

@@ -6,7 +6,7 @@ with lib;
 
 let
 
-  cfg = config.services.virtualboxGuest;
+  cfg = config.virtualisation.virtualbox.guest;
   kernel = config.boot.kernelPackages;
 
 in
@@ -15,20 +15,11 @@ in
 
   ###### interface
 
-  options = {
-
-    services.virtualboxGuest = {
-
-      enable = mkOption {
-        default = false;
-        description = "Whether to enable the VirtualBox service and other guest additions.";
-      };
-
-    };
-
+  options.virtualisation.virtualbox.guest.enable = mkOption {
+    default = false;
+    description = "Whether to enable the VirtualBox service and other guest additions.";
   };
 
-
   ###### implementation
 
   config = mkIf cfg.enable {

nixos/modules/virtualisation/virtualbox-host.nix

@@ -3,7 +3,7 @@
 with lib;
 
 let
-  cfg = config.programs.virtualbox;
+  cfg = config.virtualisation.virtualbox.host;
   virtualbox = config.boot.kernelPackages.virtualbox.override {
     inherit (cfg) enableHardening;
   };
@@ -11,7 +11,7 @@ let
 in
 
 {
-  options.programs.virtualbox = {
+  options.virtualisation.virtualbox.host = {
     enable = mkOption {
       type = types.bool;
       default = false;