Add ability to mark field as non indexed field

[r0goyal]

Considering that raw data is stored in HBase, there are scenarios where clients might want to disable indexing on certain fields (Which are huge in size like request/response body).
This data when required can be retrieved from HBase and also helps in reducing elasticsearch index size considerably.
One more reason - elastic-search places a hard limit of 32KB on any field value which is indexed otherwise document is discarded during indexing. This feature will prevent data loss in this scenario.

[santanusinha]

This is partially done by #271