Send Delete & Update in Same Request

Currently the `yz_kv:index` code uses two separate requests to a) cleanup siblings and b) index latest data.  This can be done in one request.

* Verify that the Solr XML/JSON update code performs operations in the order given.  If this doesn't hold true then 2 requests must be used to enforce correct ordering.

* Run a benchmark to compare 2 requests vs. 1 request and verify no regression (ideally, it should help performance).

I already have a branch for this code but it was written against Yokozuna when it still used XML update.  It needs to be updated for the latest.

https://github.com/rzezeski/yokozuna/tree/combine-index-and-del