Store payload in separate DB

[JonasKunze]

Currently the payload is stored in a separate index. It seems only possible to store a string within a json so we have something like following:

esClient.prepareIndex(payloadIndex, TYPE,ID)
     .setSource(
          jsonBuilder().startObject().field(PAYLOAD_FIELD, payload
     ).endObject())

In the getPayload() method we therefore have this:

response.getSourceAsMap().get(PAYLOAD_FIELD)

This seems extremely inefficient. If we want to stay with ES here and there's really no way to store a raw string, we should at least replace the getSourceAsMap() with some string operation like response.getSourceAsString().substring(X).substring(0,Y);