Add YQL table for App Links index

This YQL table lets you batch together multiple URLs to let YQL parse and cache [App Links](http://applinks.org/) metadata for you.

Example:
```sql
SELECT url, android.url FROM applinks WHERE url IN ("movietickets.com", "pinterest.com")
```

Would produce these results in XML:
```xml
<results>
    <applinks>
        <android>
            <url>movietickets://home</url>
        </android>
        <url>movietickets.com</url>
    </applinks>
    <applinks>
       <android>
           <url>pinterest://</url>
        </android>
        <url>pinterest.com</url>
    </applinks>
</results>
```

And these JSON results:
```json
{
  "results":{
    "applinks":[
      {
        "android":{
          "url":"movietickets://home"
        },
        "url":"movietickets.com"
      },
      {
        "android":{
          "url":"pinterest://"
        },
        "url":"pinterest.com"
      }
    ]
  }
}
```