Automatic merge from submit-queue

kube-proxy: add --write-config-to flag

Add --write-config-to flag to kube-proxy to write the default configuration
values to the specified file location.

@deads2k suggested I create my own scheme for this, so I followed the example he shared with me. The only bit currently still referring to `api.Scheme` is where we create the event broadcaster recorder. In order to use the custom private scheme, I either have to pass it in to `NewProxyServer()`, or I have to make `NewProxyServer()` a member of the `Options` struct. If the former, then I probably need to export `Options.scheme`. Thoughts?

cc @mikedanese @sttts @liggitt @deads2k @smarterclayton @timothysc @kubernetes/sig-network-pr-reviews @kubernetes/sig-api-machinery-pr-reviews 

```release-note
Add --write-config-to flag to kube-proxy to allow users to write the default configuration settings to a file.
```