Add services monitoring section to admin panel.

[cristianberneanu]

Oh boy, I spent way too long on this 😕... My initial approach was to create separate components for each service and use mount / unmount events to control service startup and shutdown. This would have the nice effect of easily creating a dependency hierarchy between services, allowing, for example, automatic shutdown of Metabase when PostgreSQL crashes.

I got something mostly working, but it seemed a bit too complicated and kind of weird to allow the presentation layer to control application logic. I also realized that, most likely, we don't need these complex behaviors.

In the end, I opted to simplify things significantly by making main control each service lifetime and having the Services component only reflect the current status of managed services.

This PR includes some temporary code for testing, which I'll remove when merging it with your previous changes.

[pdobacz]

LGTM! Once you merge, I'll work on adapting the init/startup scripts to this

[pdobacz]

Sorry about the conflicts - these should be relatively easy to resolve - the new TableListStep should sit in between the new Service status step and FileLoadStep. Since they're rather orthogonal, they should blend together well in the code. Let me know if you need help with any of this.

[cristianberneanu]

No worries, conflicts are par for the course at this stage.