Add websocket-powered push update notifications to admin client

[amcclain]

It would be useful to have a few examples of websocket-powered push notifications generally available for review and testing, and I think the Admin Console client could be a place that would naturally benefit.

If websockets are enabled in an app, the admin client could leverage to support push-driven refreshes / updates when:

• another admin has added or updated a key domain object - e.g. AppConfig, Preference.
• a new memory or connection pool snapshot has been taken, triggering immediate target refresh on those tabs if active.
• a new client error was recorded
• a new status monitor run completed