title: Translate filter with external dictionary and refresh behaviour
body: <p>I want to extract mapping to external dictionaries. Below is example of one of my translate filter configurations.</p>
  
  <pre><code>translate 
  {
      destination =&gt; "target_field"
      field =&gt; "source_field"
      dictionary_path =&gt; "mapping.yml"
      exact =&gt; true
      refresh_behaviour =&gt; "replace"
  }
  </code></pre>
  
  <p>When I verify it with</p>
  
  <pre><code>\bin\logstash.bat --config.test_and_exit -f .\logstash-6.2.2\logstash-conf\2filters.conf
  </code></pre>
  
  <p>I get error message</p>
  
  <pre><code>[ERROR][logstash.filters.translate] Unknown setting 'refresh_behaviour' for translate
  </code></pre>
  
  <p>But this is how documentation shows it should be done - <a href="https://www.elastic.co/guide/en/logstash/6.2/plugins-filters-translate.html#plugins-filters-translate-refresh_behaviour" rel="nofollow noreferrer">https://www.elastic.co/guide/en/logstash/6.2/plugins-filters-translate.html#plugins-filters-translate-refresh_behaviour</a></p>
  
  <p>I am using logstash-6.2.2.</p>