title: Find documents with field that doesn't exist or field is less than value
body: <p>I have some employees and am trying to find those people that either don't have a birthday entered or have a birthday earlier than 1963-03-01. I have:</p>
  
  <pre><code>GET employees/_search
  {
    "query": {
      "bool": {
        "must_not": {
          "exists": {
            "field": "birthday"
          }
        },
        "filter": {
          "range": {"birthday": {"lte": 19630301}}
        }
      }
    }
  }
  </code></pre>
  
  <p>Right now I have 250 employees and none of them have a birthday field yet this query returns 0 results. </p>