Add option to enable a simple CORS implementation for the api server

Related to https://github.com/GoogleCloudPlatform/kubernetes/issues/1128
Ah! I missed this, sorry. Making a NewLogged here is problematic-- imagine someone calling LogOf(w) multiple times, and also consider that because w is not a pointer, the logger that you make will never print anything because its WriteHeader method will never be called. My preferred solution is to return an instance of some type that looks like this:

```
type passthroughLogger struct{}

 // Addf logs info immediately.
 func (passthroughLogger) Addf(format string, data ...interface{}) {
 	glog.Infof(format, data...)
 }
```

You'll have to change the return value of LogOf to be an interface type that defines the Addf method.