Supporting writeBulk and readBulk

[pencal]

I am thinking about adding writeBulk and readBulk operations to ndbench. My thought is to add the bulkSize parameter in startWrites and startReads and default it to 1, which falls back to writeSingle and readSingle. Any comments?

[buildlackey]

To keep things consistent we'd have to update Elastic search plugin to use the new 'bulkSize' parameter instead of the getBulkWriteBatchSize() param that it now uses. Also.. I am implementing writeSingle for elastic search such that it actually does bulk write based on getBulkWriteBatchSize(). If this change goes in we should file a bug to do the work to make ES_REST plugin consistent w/ this new approach.

[buildlackey]

I would recommend NOT closing this bug until the above issue is addressed.. Otherwise things will get inconsistent.