[WIP][SPARK-2097][SQL] UDF Support

Remaining:
 - [x] Python Support
 - [x] Python Test cases
 - [x] Move out of hive
 - [ ] scala Test cases
 - [ ] Input coercion?
But that is okay right?  Since I've now changed registerFunction to use BatchedSerializer(PickleSerializer) always as you recommended?  I can add a comment to that effect.