Add OG object type filter. Map built-in post formats to OG global type equivalents. Attach audio and video

The Open Graph protocol code would always assume a single post is an [Open Graph article](https://developers.facebook.com/docs/reference/opengraph/object-type/article "Facebook Open Graph object: article"). Treat a [post format](http://codex.wordpress.org/Post_Formats "WordPress post formats") of image as a [photo object](https://developers.facebook.com/docs/reference/opengraph/object-type/photo "Facebook Open Graph: photo object"), post format of video as a [video.other object](https://developers.facebook.com/docs/reference/opengraph/object-type/video.other "Facebook Open Graph: video object"). The resulting Open Graph object type is passed through a new WordPress filter, `facebook_og_type`, for an early override of a specific post's Open Graph type affecting type-specific properties.

Posts declared as an Open Graph object other than article are posted to an author's Facebook timeline using the generic feed endpoint instead of the news.publishes Open Graph action (if news.publishes is available as the result of an opt-in after additional setup).

Expand the list of built-in CURIE prefix mappings: [business](https://developers.facebook.com/docs/reference/opengraph/object-type/business.business "Facebook Open Graph business.business object"), [event](https://developers.facebook.com/docs/reference/opengraph/object-type/event "Facebook Open Graph event object"), [fitness](https://developers.facebook.com/docs/reference/opengraph/object-type/fitness.course "Facebook Open Graph fitness.course object"), [product](https://developers.facebook.com/docs/reference/opengraph/object-type/product "Facebook Open Graph product object"), [restaurant](https://developers.facebook.com/docs/reference/opengraph/object-type/restaurant.restaurant "Facebook Open Graph restaurant.restaurant object").

Express video attachments as Open Graph protocol video structured properties for `video.other` objects.

Add Open Graph protocol audio structured properties for the audio built-in post format.

Audio and video child posts are discovered using the [get_attached_media](http://codex.wordpress.org/Function_Reference/get_attached_media "WordPress Codex: get_attached_media function") introduced in WordPress 3.6 if present.