Theme editor changes

[muskgupta]

Description

This PR is to merge ThemeEditorPOC branch with master.

Related Issue

Theme Editor Feature

How Has This Been Tested?

Tested all changes on ThemeEditorPOC branch and locally as well.

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have signed the Adobe Open Source CLA.
• [ ] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes and the overall coverage did not decrease.
• [ ] All unit tests pass on CircleCi.
• [ ] I ran all tests locally and they pass.