Refactor management of application settings

[dascentral]

There are two elements to this issue:

1. Now that I've installed mackup, I need to understand how to use it
2. My developer tools have settings spread across iCloud, Google Drive, and this repo. Can they all be centralized here?

[dascentral]

I am considering task no. 2 "complete" following a refactor of other scripts. All items that were at iCloud are now at Google Drive. Unclear if I want to move those to this repository but I'll tackle that another day.