Move ScriptTransformation into the appropriate place.

Author: Reynold Xin <rxin@apache.org>

Closes #1162 from rxin/script and squashes the following commits:

2c836b9 [Reynold Xin] Move ScriptTransformation into the appropriate place.

(cherry picked from commit d4c7572dba1be49e55ceb38713652e5bcf485be8)
Signed-off-by: Reynold Xin <rxin@apache.org>
[SQL] Use hive.SessionState, not the thread local SessionState

Note that this is simply mimicing lookupRelation(). I do not have a concrete notion of why this solution is necessarily right-er than SessionState.get, but SessionState.get is returning null, which is bad.

Author: Aaron Davidson <aaron@databricks.com>

Closes #1148 from aarondav/createtable and squashes the following commits:

37c3e7c [Aaron Davidson] [SQL] Use hive.SessionState, not the thread local SessionState

(cherry picked from commit 2044784915554a890ca6f8450d8403495b2ee4f3)
Signed-off-by: Reynold Xin <rxin@apache.org>