title: spring-data-elasticsearch - @Field / FieldIndex.not_analyzed ignored
body: <p>I am using spring-data-elasticsearch 1.1.2.  I am trying to use java annotation to specify that a field should not be analyzed.</p>
  
  <p>I use the following annotation: 
      @Field(index = FieldIndex.not_analyzed)
      private String category;</p>
  
  <p>The generated mapping does not include "index":"not_analyzed" for this field:</p>
  
  <pre><code>    "properties" : {
        "category" : {
          "type" : "string"
        },
        ...
  </code></pre>
  
  <p>I am having no luck finding helpful documentation about how to do this but it looks like it should work.</p>
  
  <p>Should it work?  Where can i find more information?  How best to debug?</p>
  
  <p>Thank you.</p>
  
  <p>update: problem also present with the latest 1.2.0 version.</p>