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

Remaining:
 - [x] Python Support
 - [x] Python Test cases
 - [x] Move out of hive
 - [ ] scala Test cases
 - [ ] Input coercion?
Oh actually, its correct as is.  The `.select('value)` is producing a row with only a single string value.  The toString is not explicitly needed though.