Add feedback

[aentwist]

Is your feature request related to a problem? Please describe.
As a user I value feedback. I need to know what the app is doing.

Describe the solution you'd like
Move from console-only feedback to a new response message type that provides async status updates. These can then be used to update the UI state, adding running states, status messages, etc.

Describe alternatives you've considered
Move to gRPC and use async requests