Admin - Annotation pipeline runs / celery jobs

Somewhat related to #1086

* On annotation pipeline run page - show celery jobs and a big warning if no jobs found
* Maybe on server status page or login for admins?

Problem is to fix this:

If you shut down the VM while there are running celery jobs they will not be restarted automatically.
This is most likely to happen with annotation.
What this will look like is that, upon restart:
* The annotation pipeline runs page shows a number of queued/running annotation runs
* There are no running perl/VEP tasks in top, and no celery workers running or queued. To see this, go as admin to "server status" page (click user icon top right, then "server status")