feat: variants custom stickiness

[daveleek]

Description

This is a Work In Progress
This PR intends to implement issue #72. Custom stickiness for variants.

Fixes # (issue)
#72

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• VariantUtilsTests.Custom_Stickiness_CustomField_528_Yields_Blue
• VariantUtilsTests.Custom_Stickiness_CustomField_16_Yields_Blue
• VariantUtilsTests.Custom_Stickiness_CustomField_198_Yields_Red
• VariantUtilsTests.Custom_Stickiness_CustomField_43_Yields_Green
• VariantUtilsTests.Custom_Stickiness_CustomField_112_Yields_Yellow

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[chriswk]

LGTM