Translate columnar RPC to row based API in C++ client

The Java client is capable of receiving the columnar based RPC row format response and then translating it for use in the row based API. This is useful because it allows the more efficient (wire size and server CPU usage) format to be use without code changes in client applications.

This would be especially beneficial for Apache Impala in cases where an external cluster is accessing Kudu data remotely.

The Java client commit for reference: https://github.com/apache/kudu/commit/34e85622f37f88b0436d9ba51df7592bf0e159de