Add support for external logging services

[rglover]

When Joystick Deploy launches, it will have its own logs feature on the disk of instances, but it'd be good to support third-party logging tools at the app-level.

Not 100% sold, but may be good to offer a logs option for @joystick.js/node which pre-configures drivers for popular services based on your settings. If you say something like...

node.app({
  logs: {
    provider: 'sentry',
    credentials: {
      apiKey: '',
    },
    options: {}
  },
});

Sentry would automatically be run on app startup and logs would be routed to the passed API key.

[rglover]

Don't forget about the built-in event hooks. May be better to document common services being used there.