Add interactions to comments for likes

[tclaus]

To implement diaspora/diaspora#8203 a comment can have one or more likes.
A comment should have a interactions node, with a likes array and likes_count. Similar to post.interactions.
"interactions": { "likes": [..], "likes_count": 42 }

Is this OK to extend a comment json this way?

[Flaburgan]

Yep looks good to me, and as @jhass also thumbed up I would say it's fine. Would you mind opening a pull request?

[tclaus]

Wat comes into my mind - for the API part, the like has an author, the author has an avatar, the avatar is an image, or a list of three different avatars.
I think for the API the avatar may only be one image (the small one), and for the backbone(?) all thee kinds of profile images?