Refactor api/webapp for clarity.

- Rename API methods to list + add (using set + get might be
  confusing for them as they're very generic terms used in the API)

- Break apart monolithic function in flask app to have separate
  view callables for each view.

- Update README to show new API.
Switch to "add" API.
Remove method-y self in API.
Cleanup.
Refactor JS for clarity.
Add whitespace for readability to JS.