SocialContextOperations: return user picture in getAllMutualFriends response

[troig]

According to the graph API documentation, facebook is returning the user picture in all mutual friends response.
This is very usefull, specially for those users that don't use the app (now only the name user can be retrived through spring-social-facebook)

Example response from facebook:

{
  "context": {
    "all_mutual_friends": {
      "data": [
        {
          "name": "Non App User",
          "token": "QVNscHZAQM0w5ZAS0yY1ZAuak45aVQ3Y05sbWtMb0x0eEZAWM0d6WFBoOUM0UWVfUnpOdkZAsUXhaM0tqMEdOWFJsNjlPUFpWVHRNMVdUNk5LYk5pcEhpS01HMDRnV2wzYlNZAU2RhTGRGWW1Eb0lmc2cZD",
          "picture": {
            "data": {
              "is_silhouette": true,
              "url": "https://scontent.xx.fbcdn.net/v/t1.0-1/c15.0.50.50/p50x50/1379841_10150004552801901_469209496895221757_n.jpg?oh=7d1a30477a7ac57749e72821136a7090&oe=5865EA33"
            }
          }
        },
        {
          "name": "APP User",
          "token": "QVNsY0NnT3JUTkJZAMXE2eUdjMEJFREp0ZA2RmUHVBTUtTOGltZA0xKal81THQtamdtRFVRS1gtdDI0TnJfVEtLamlKQmxpZAVY0R2pROVRET3lVLVhQbjdqZAGFySDZAWdUtONHhUcnU1S2tURzBLcFEZD",
          "picture": {
            "data": {
              "is_silhouette": false,
              "url": "https://scontent.xx.fbcdn.net/v/t1.0-1/c50.50.621.621/s50x50/397837_10150472809100036_1549619425_n.jpg?oh=c06f0c22938d845d8ea764d21ce35d62&oe=58690A97"
            }
          },
          "id": "10153377367605036"
        }
      ]
      ...
    }
  }
}

Maybe a choice could be returning the user picture in FacebookObject extra data..

Something like that (example for a non app user):

{
 "id": null,
 "name": "Non App user name",
 "extraData": {
   "id": "picture",
   "value": "https://scontent.xx.fbcdn.net/v/t1.0-1/c15.0.50.50/p50x50/1379841_10150004552801901_469209496895221757_n.jpg?oh=7d1a30477a7ac57749e72821136a7090&oe=5865EA33"
 }
}