Minimal user workflow for download -> edit -> upload -> review -> commit

[themightychris]

Using the organizations list within the brigade-project-index#index/v1 tree as a test case, smooth out the end-user workflow for:

1. Open the organizations list in the gitsheets UI
2. Download the organizations list to CSV
3. Make changes to the CSV file offline
4. Upload modified CSV through gitsheets UI
5. Review staged changes through gitsheets UI
6. Commit staged changes with either default commit message or custom commit message