Feature/add alternate names

[jazzyclimber]

Types of change

• [ ] Bug fix (change which fixes an issue)
• [ x ] Enhancement (change which improves upon an existing feature)
• [ ] New feature (change which adds new functionality)

Description

Add initial support for alternate_name field. This is only added into theme settings and only for primary_color, secondary_color, body_font, heading_font

746 (enterprise)

Checklist

• [ x ] I have read the CONTRIBUTING document.
• [ x ] My code follows the style guide requirements.
• [ x ] I have thoroughly tested my change.

People to notify