Stop printing stack traces with UI error feedback

[wesgarland]

niim> c
Thrown:
Error: Use `run` to start the app again.
    at Promise (/Users/wes/.nvm/versions/node/v10.20.1/lib/node_modules/niim/lib/internal/inspect_client.js:238:16)
    at new Promise (<anonymous>)
    at Client.callMethod (/Users/wes/.nvm/versions/node/v10.20.1/lib/node_modules/niim/lib/internal/inspect_client.js:236:12)
    at Proxy.callVirtualMethod (/Users/wes/.nvm/versions/node/v10.20.1/lib/node_modules/niim/lib/_inspect.js:143:23)
    at Object.get cont [as cont] (/Users/wes/.nvm/versions/node/v10.20.1/lib/node_modules/niim/lib/internal/inspect_repl.js:956:25)
niim> 

This could probably use a nicer message - but we definitely need to get rid of that stack trace. It's in the way and adds nothing.