title: ES case insensitive boolean field
body: <p>I have 1m record where one column is boolean. It contains three values. <code>FALSE, TRUE, [Blank]</code>.</p>
  
  <p>I want this field to be treated as boolean. Due to the case, it is not treated as boolean. I understand that ES supports true or "true" as boolean and no analyser on this.</p>
  
  <p>Is there any other way to handle my records? Records are dynamic too. As load arrives, it has to be stored appropriately.</p>