Analytics: Aggregation queries fail

[SuzanaK]

The queries in the Analytics Chapter fail when executed with this error message:

{
   "error": {
      "root_cause": [
         {
            "type": "illegal_state_exception",
            "reason": "Field data loading is forbidden on [interests]"
         }
      ],
      "type": "search_phase_execution_exception",
      "reason": "all shards failed",
      "phase": "query",
      "grouped": true,
      "failed_shards": [
         {
            "shard": 0,
            "index": "megacorp",
            "node": "1JKN2iW3S_6fveH4AOQJtQ",
            "reason": {
               "type": "illegal_state_exception",
               "reason": "Field data loading is forbidden on [interests]"
            }
         }
      ]
   },
   "status": 500
}

The reason is that _raw must be attached to the field name - see this this issue on Elasticsearch for an explanation.