Admin - See all running sessions

As an admin, I want to see all running sessions. A session is created when the user starts to use the application, and it remains active until it gets killed due to time out (time out is out of scope and will be managed by Theia.cloud).
For every session, I can see details about the session (covered in #11 )
In the future I can also trigger actions on the sessions (covered in #14 )
Please consider that filtering and sorting might need to be supported in the future.