[SPARK-1964][SQL] Add timestamp to HiveMetastoreTypes.toMetastoreType

Author: Michael Armbrust <michael@databricks.com>

Closes #1061 from marmbrus/timestamp and squashes the following commits:

79c3903 [Michael Armbrust] Add timestamp to HiveMetastoreTypes.toMetastoreType()

(cherry picked from commit 1c2fd015b05b65abc83c4874ada825deac578af8)
Signed-off-by: Michael Armbrust <michael@databricks.com>