Expanding Spark ML under Different Namespace

This ticket is corresponding to a previous email thread in the dev list: [Spark Namespace]: Expanding Spark ML under Different Namespace?

The concern is about making some access modifier of some classes/trait from "private [spark]" to public.

Right now, the options to solve this issues are:
1. write or copy your own implementations
2. work under org.apache, but have some comments to address this issue

Details can be found in the dev list email archive.