add REST documentation for content module

I think it returns the full content profile. (If not, the model for `BasicContent` is missing quite a bit.)

```
{
  "tenant": {
    "alias": "Tenant",
    "displayName": "Tenant"
  },
  "id": "c:Tenant:-J25URDob",
  "visibility": "public",
  "displayName": "New Name",
  "description": "",
  "resourceSubType": "link",
  "createdBy": {
    "tenant": {
      "alias": "Tenant",
      "displayName": "Tenant"
    },
    "id": "u:Tenant:xylrEJMQDp",
    "displayName": "User One",
    "visibility": "public",
    "email": "userone@not.iz",
    "locale": "en_US",
    "publicAlias": "User One",
    "picture": {
      "small": "/api/download/signed?uri=local%3Au%2FTenant%2Fxy%2Flr%2FEJ%2FMQ%2FxylrEJMQDp%2Fprofilepictures%2F1407435494766%2Fsmall.jpg&expires=1409184000000&signature=d5f4f46108bf70ebe0955f91ead465361ed23cb9",
      "medium": "/api/download/signed?uri=local%3Au%2FTenant%2Fxy%2Flr%2FEJ%2FMQ%2FxylrEJMQDp%2Fprofilepictures%2F1407435494766%2Fmedium.jpg&expires=1409184000000&signature=dc576e42c30b81202f07aacc70b0b421b79acb63",
      "large": "/api/download/signed?uri=local%3Au%2FTenant%2Fxy%2Flr%2FEJ%2FMQ%2FxylrEJMQDp%2Fprofilepictures%2F1403542881749%2Flarge.jpg&expires=1409184000000&signature=e0e32ea524f85b9fbfcede8f8252e2553b92fcdc"
    },
    "profilePath": "/user/Tenant/xylrEJMQDp",
    "resourceType": "user",
    "notificationsUnread": 0,
    "notificationsLastRead": 1407418942947,
    "acceptedTC": 1400523404749,
    "lastModified": 1407435494767,
    "emailPreference": "daily"
  },
  "created": "1407938305085",
  "lastModified": "1408018846952",
  "profilePath": "/content/Tenant/-J25URDob",
  "resourceType": "content",
  "latestRevisionId": "rev:Tenant:-1x39LRwib",
  "previews": {
    "embeddable": false,
    "httpsAccessible": true,
    "status": "done",
    "total": 4,
    "thumbnailUrl": "/api/download/signed?uri=local%3Ac%2FTenant%2F-J%2F25%2FUR%2FDo%2F-J25URDob%2Fpreviews%2Frev-Tenant--1x39LRwib%2Fthumbnail.jpg&expires=1409184000000&signature=c57ab5cfd9d64c6c671d7d3305bb42ec066efbae",
    "smallUrl": "/api/download/signed?uri=local%3Ac%2FTenant%2F-J%2F25%2FUR%2FDo%2F-J25URDob%2Fpreviews%2Frev-Tenant--1x39LRwib%2Fsmall.png&expires=1409184000000&signature=0be37a303c93e305d09724f36bf1e835f72e607e",
    "mediumUrl": "/api/download/signed?uri=local%3Ac%2FTenant%2F-J%2F25%2FUR%2FDo%2F-J25URDob%2Fpreviews%2Frev-Tenant--1x39LRwib%2Fmedium.png&expires=1409184000000&signature=cdf3bf64b1389c45ad0dedd7e108373c6efb3d11",
    "largeUrl": "/api/download/signed?uri=local%3Ac%2FTenant%2F-J%2F25%2FUR%2FDo%2F-J25URDob%2Fpreviews%2Frev-Tenant--1x39LRwib%2Flarge.png&expires=1409184000000&signature=d79ee51afa36ad84a8a907c9e0ab96669a49cd12"
  },
  "link": "http://www.google.com",
  "signature": {
    "expires": 1408104000000,
    "signature": "54ee273fa9a736dd862987e46215264285f817be"
  },
  "isManager": true,
  "canShare": true
}
```