Vectorize Druid Storage Handler Reader

This patch aims at adding support for vectorize read of data from Druid to Hive.

Gopal V suggested that this will improve the performance of the top level operators that supports vectorization.

As a first cut am just adding a wrapper around the existing Record Reader to read up to 1024 row at a time. 

Future work will be to avoid going via old reader and convert straight the Json (smile format) to Vector primitive types.