Service definition export format (#2397)

Three main goals:

1. In the front end:
      a. Show form fields and automatically assemble badge URLs (#701)
      c. Group together examples for the same service
      b. Show deprecated services
2. Make it easy to changing the schema of `examples`, thanks to 100% validation. One challenge with frameworks is that when there are typos things fail silently which is pretty unfriendly to developers. The validation should really help with that. (This caught one bug in AUR, though I fixed it in #2405 which landed first.)
3. Produce a service definition export for external tool builders. (#776)
4. Build toward harmony between the front-end data structure and the `examples` key in the service classes. I aliased `staticPreview` to `staticExample` which starts this process.

The old format:

- Lacked a consistent machine-readable representation of the fields.
- Flattened multiple examples for the same service were flattened.
- Excluded deprecated services.

The new format improves a few things, too:

- It cleans up the naming. Since this file evolved over time, the names were a bit muddled (i.e. what was an example vs a preview).
- It duplicated information (like `.svg`). (I can imagine dropping the `.svg` from our badge URLs someday, which would make the URLs easier to read and maintain.)
- For a human reading the YAML file, providing the static example as a deconstructed object is more readable.

Here are a couple snippets:

```yml
  - category: build
    name: AppVeyorCi
    isDeprecated: false
    route:
      format: '([^/]+/[^/]+)(?:/(.+))?'
      queryParams: []
    examples:
      - title: AppVeyor
        example: {path: /appveyor/ci/gruntjs/grunt, queryParams: {}}
        preview: {label: build, message: passing, color: brightgreen}
        keywords: []
      - title: AppVeyor branch
        example: {path: /appveyor/ci/gruntjs/grunt/master, queryParams: {}}
        preview: {label: build, message: passing, color: brightgreen}
        keywords: []
  - category: downloads
    name: AmoDownloads
    isDeprecated: false
    examples:
      - title: Mozilla Add-on
        example: {path: /amo/d/dustman, queryParams: {}}
        preview: {path: /amo/d/dustman, queryParams: {}}
        keywords: [amo, firefox]
```