Refactor customization config to use key:value

[davidferlay]

Observed

• Customization variable keys are set in local config file but values are fetched from set group_vars yaml file
• This behavior works well in Ansible based projects using group_vars but does not apply so well to others

Expected

• It would be great to simplify customization settings by using a key:value mechanism :

web:
  vars_file: platform/group_vars/platform/vars.yaml
  variables:
    - plasmactl_web_ui_platform_name: "ABC"