Refactor variable naming to match new variable schema

# Refactor variable naming to match new variable schema

Status: **Opened for visibility**
Reviewers: @ry5n @jeffkamo 

## Changes
1. Changed all variables to match #29's outlined schema
1. Updated some comments to better address the new format
1. Renamed body-color to background-color to better match application.
1. Reordered the placement of some properties to fix issue #1   

## Notes
- This fixes #29.
- This does not fix any issues like whether our neutrals are declared in the right order or whether we should use color definition variables. This simply moves towards a more sane variable schema as outlined in #29.