[WIP] Add support for Config{} to kubecfg

This PR will allow users to use simple JSON file with arrays of Kubernetes objects (services, pods, replicationControllers) as a parameter for `kubecfg -c config.json apply` command.

The [example JSON](https://github.com/mfojtik/kubernetes/blob/config/examples/config/guestbook.json) file in `examples/config/guestbook.json` contains all objects required for deploying the [guestbook example](https://github.com/GoogleCloudPlatform/kubernetes/tree/master/examples/guestbook).
I would consider using this sort of struct for this purpose. This allows each object in the file to be independently versioned and typed, which means it's not confined to the three here.

```
type APIObjectList struct {
  JSONBase `yaml:",inline" json:",inline"`
  Items    []APIObject `yaml:"items,omitempty" json:"items,omitempty"`
}
```
(APIObject needs some fixes to ensure that it continues to use the specific Codec, but that won't matter until we have multiple versions.)