Change QueryResult to retain column value types

https://issues.cask.co/browse/CDAP-384
Since a Hive query result row only contains objects of primitive types, we define a new QueryResult.ObjectResult that holds the type and the primitive value.

Bamboo build: https://builds.cask.co/browse/CDAP-DUT114
You're right we may not need the type information, so we could go with your solution 2).