title: How to really reindex data in elasticsearch
body: <p>I have added new mappings (mainly not_analyzed versions of existing fields) I now have to figure out how to reindex the existing data. I have tried following the guide on elastic search website but that is just too confusing. I have also tried using plugins (elasticsearch-reindex, allegro/elasticsearch-reindex-tool).
  I have looked at <a href="https://stackoverflow.com/questions/29508955/elasticsearch-reindexing-your-data-with-zero-downtime">ElasticSearch - Reindexing your data with zero downtime</a> which is a similar question. I was hoping to not have to rely on external tools (if possible) and try and use bulk API (as with original insert)</p>
  
  <p>I could easily rebuild the whole index as it's a read only data really but that wont really work in the long term if I should want to add more fields etc etc when I'm in production with it. 
  I wondered if there was anyone who knows of an easy to understand/follow solution or steps for a relative novice to ES. I'm on version 2 and using Windows.</p>