Meta profile details

The basic profile has been completely removed, and most of the fields moved to the meta post. An optional parameter set when requesting a single post or list of post data allows apps to receive an object containing these profile fields for each entity that published an included post, as well as mentioned entities.

**List Page**
```json
{
  "pages": {},
  "posts": ["..."],
  "refs": ["..."],
  "meta": {
    "https://jonathan.tent.is": {
      "name": "Jonathan Rudenberg",
      "location": "The Internet",
      "avatar_digest": "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae",
    }
  }
}
```

**Single Post**
```json
{
  "post": {},
  "refs": ["..."],
  "meta": {
    "https://jonathan.tent.is": {
      "name": "Jonathan Rudenberg",
      "location": "The Internet",
      "avatar_digest": "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae",
    }
  }
}
```


See also tent/tent-schemas#7.