Update list views based on events from event bus

[JasonWeill]

Problem

After creating a new job or job definition, if the back-end is slow to fulfill the creation request, the user might have to manually reload the list view to see their newly-created item.

Proposed Solution

Connect to JupyterLab's event bus, when it is available. Update the list views when a new job or job definition is created.

Additional context

Event bus code lives in https://github.com/jupyter/jupyter_events