title: Failed to make a string raw for date (Elastticsearch)
body: <p>I want to search a date field without using range. So I decided to make a string raw to search into it as it is text:</p>
  
  <pre><code> "myDate": {
                              "type": "date",
                              "format": " yyyy-MM-dd || yyyy-MM || Y ||date_hour_minute_second",
                              "fields": {
                                  "raw": {
                                      "type": "string",
                                      "index": "not_analyzed",
                                      "null_value": "",
                                      "doc_values": true
                                  }
                              }
                          }
  </code></pre>
  
  <p>But it shows up in kopf nothing for myDate.raw. Any idea?</p>
  
  <p>Thanks</p>