title: JsonPath syntax for "does not include", or negative matching?
body: <p>Consider this sample JSON:</p>
  
  <pre><code>{
    "thing": [
      {
        "name": "foo",
        "flag": "yep"
      },
      {
        "name": "bar"
      },
      {
        "name": "baz",
        "flag": "nope"
      }
    ]
  }
  </code></pre>
  
  <p>If I wanted to find all the 'name' elements that DID have a corresponding 'flag', I could use something like this:</p>
  
  <pre><code>$.thing[?(@.flag)].name
  </code></pre>
  
  <p>I would get back the results:</p>
  
  <pre><code>'0' =&gt; "foo"
  '1' =&gt; "baz"
  </code></pre>
  
  <p>But what if I wanted to find all the 'name' elements that DID NOT have a corresponding 'flag'?</p>
  
  <p>(for the purposes of this question, I don't care about the value of 'flag', only whether or not it's present)</p>