Serialization features bc

[saif-ellafi]

Description

Improves memory consumption. Creates a new Param like concept called Feature which stores model information in a more scalable way.

Motivation and Context

Out of driver RAM situations when dealing with pipelines containing large training corpus

How Has This Been Tested?

Benchmarks made, comparing broadcasting vs non broadcasting versions. Serialization with KRYO as opposed to 1.2.4. Memory consumption reduced by many factors.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Code improvements with no or little impact
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING page.
• I have added tests to cover my changes.
• All new and existing tests passed.