title: using spring-data-elasticsearch, how to update a field mapping?
body: <p>I am usign spring-data-elasticsearch 2.1.4.RELEASE , How can I update a field mapping for a type using ElasticsearchOperations?</p>
  
  <p>when I try  operations.putMapping(EsJob.class); again ,there is exception:
  because the field createdBy already exist, but I want to update it .
  Anyone have a better solution for this?</p>
  
  <pre><code>Servlet.service() for servlet [dispatcher] in context with path [/api] threw exception [Request processing failed; nested exception is java.lang.IllegalgumentException: Mapper for [createdBy] conflicts with existing mapping in other types:
  [mapper [createdBy] has different [store] values, mapper [createdBy] has different [analyzer]]] with root cause
  java.lang.IllegalArgumentException: Mapper for [createdBy] conflicts with existing mapping in other types:
  [mapper [createdBy] has different [store] values, mapper [createdBy] has different [analyzer]]
          at org.elasticsearch.index.mapper.FieldTypeLookup.checkCompatibility(FieldTypeLookup.java:153)
          at org.elasticsearch.index.mapper.FieldTypeLookup.copyAndAddAll(FieldTypeLookup.java:115)
          at org.elasticsearch.index.mapper.MapperService.merge(MapperService.java:381)
          at org.elasticsearch.index.mapper.MapperService.merge(MapperService.java:320)
          at org.elasticsearch.cluster.metadata.MetaDataMappingService$PutMappingExecutor.applyRequest(MetaDataMappingService.java:306)
          at org.elasticsearch.cluster.metadata.MetaDataMappingService$PutMappingExecutor.execute(MetaDataMappingService.java:230)
          at org.elasticsearch.cluster.service.InternalClusterService.runTasksForExecutor(InternalClusterService.java:468)
          at org.elasticsearch.cluster.service.InternalClusterService$UpdateTask.run(InternalClusterService.java:772)
          at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:231)
          at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:194)
          at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
          at java.lang.Thread.run(Thread.java:748)
  </code></pre>