Add a hot restart tool

[jakemac53]

Sometimes hot reload isn't quite enough, especially at early stages of app development. We should expose hot restart as well.

[sethladd]

This came up today, it would be good to have. We have hot restart, but not all changes are hot restartable.

work around is: shut down app, re-run app. Which works, of course, but not ideal

[sethladd]

amazing!