[SQL] SPARK-1732 - Support for null primitive values.

I also removed a println that I bumped into.

Author: Michael Armbrust <michael@databricks.com>

Closes #658 from marmbrus/nullPrimitives and squashes the following commits:

a3ec4f3 [Michael Armbrust] Remove println.
695606b [Michael Armbrust] Support for null primatives from using scala and java reflection.

(cherry picked from commit 3c64750bdd4c2d0a5562f90aead37be81627cc9d)
Signed-off-by: Matei Zaharia <matei@databricks.com>