In goal terminology, be consistent in usage of "ID" instead of "index"

**Context**
I create an app using `goal app create` and it tells me "Created app with app index 2". A minute later I go to call the app using goal and the command has `--app-id`. This may seem minor, but this inconsistent terminology can cause confusion and should be cleaned up.

**What are you looking for?**
find all occurrences of referring to app "index" in goal outputs, and update them to "ID" instead.