Expose Document Relationships with an enricher

"relations": {
    "entity-type": "statementInfos",
    "entries": [
      {
        "incoming": true,
        "outgoing": false,
        "name": "depends_on",
        "comment": "Nuxeo LTS 2010",
        "creationDate": "2015-11-10T16:51:21.13Z",
        "modificationDate": "2015-11-10T16:51:21.13Z",
        "author": "system",
        "object": {
          "entity-type": "document",
          "repository": "default",
          "uid": "837faafd-7505-432c-92ea-53ada7f1c077",
          "path": "/default-domain/workspaces/Nuxeo/nuxeo-7.10",
          "type": "Release",
          "state": "project",
          "parentRef": "837faafd-7505-432c-92ea-53ada7f1c077",
          "isCheckedOut": true,
          "changeToken": "1424105481137",
          "title": "Nuxeo LTS 2010",
          "lastModified": "2015-11-10T16:51:21.13Z",
          "facets": [
            "Folderish",
            "SuperSpace",
            "NotCollectionMember"
          ]
        }
      }
    ]
  }