Automatic merge from submit-queue

Improvements to CLI usability and maintainability

Improves `kubectl` from an usability perspective by

1. Fixing how we handle terminal width in help. Some sections like the flags use the entire available width, while others like long descriptions breaks lines but don't follow a well established max width (screenshot below). This PR adds a new responsive writer that will adjust to terminal width and set 80, 100, or 120 columns as the max width, but not more than that given POSIX best practices and recommendations for better readability.
![terminal_width](https://cloud.githubusercontent.com/assets/158611/19253184/b23a983e-8f1f-11e6-9bae-667dd5981485.png)
2. Adds our own normalizers for long descriptions and cmd examples which allows us better control about how things like lists, paragraphs, line breaks, etc are printed. Features markdown support. Looks like `templates.LongDesc` and `templates.Examples` instead of `dedent.Dedend`.
3. Allows simple reordering and reuse of help and usage sections.
3. Adds `verify-cli-conventions.sh` which intends to run tests to make sure cmd developers are using what we propose as [kubectl conventions](https://github.com/kubernetes/kubernetes/blob/master/docs/devel/kubectl-conventions.md). Just a couple simple tests for now but the framework is there and it's easy to extend.
4. Update [kubectl conventions](https://github.com/kubernetes/kubernetes/blob/master/docs/devel/kubectl-conventions.md) to use our own normalizers instead of `dedent.Dedent`.

**Release note**:
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```release-note
Improves how 'kubectl' uses the terminal size when printing help and usage.
```

@kubernetes/kubectl