Currently pyspark can only call the builtin java UDF, but can not call custom java UDF. It would be better to allow that. 2 benefits:
* Leverage the power of rich third party java library
* Improve the performance. Because if we use python UDF, python daemons will be started on worker which will affect the performance.

Author: Jeff Zhang <zjffdu@apache.org>

Closes #9766 from zjffdu/SPARK-11775.