Custom Data Type with Transformer: UdfTransformer

Overview

1. Create a custom data type to store MLeap UserDefinedFunction factories
2. Create a transformer that uses these factory methods to transform leap frames
3. Create a Spark transformer that uses these factory methods to transform Spark data frames
4. Implement serialization for both MLeap and Spark transformer
5. Add our serializers to the appropriate reference.conf files
6. Put everything together into a pipeline that can be used by Spark or MLeap