More Open Graph article metadata

[sybrew]

From marty's question:

Facebook specifies more supported meta tags than TSF outputs. Let's improve that.

These two can be marked up via WordPress' own data:

1. article:section can be related to the (Post) Category name.
2. article:tag can be used as an array displaying the Post Tag names.

This implementation is easier done than said. For this, we will use the term names, not the SEO meta names.

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The tags below are still open to discussion, and will have their own issue created when the above is implemented.

Tags that are App, Audio, Video, or Age-specific have no home in TSF's core plugin and should be handled through extensions.

Tags like og:ttl and og:determiner are too verbose, and are automatically determined by Facebook when omitted.

og:see_also is very interesting, given we supply a "related article" URL (under the Structure tab). I'll see if this feature is useful for other metadata prior implementing it.

og:rich_attachment is enabled by default and I believe it acts as a "disabler"; i.e. for if you don't want Facebook to markup your content when shared.

[sybrew]

Moved to v3.2, it takes too much time testing this.

[sybrew]

After some digging for links shared with article:tag and testing them on Facebook's platform, I've found no evidence in Facebook that they're utilizing these tags.