GUI highlighting of running VMs

[marcox]

I would find very useful, in the GUI Manager, some graphic indicators showing which VMs are running (for example, red bullets on the right side of the VMs' names) or, at least, a single indicator (maybe near the top command buttons) which stays on while one or more VMs are running.
When using multiple VMs as I do, often keeping some of them minimized, it would be useful, for example before shutting down the host system, to check at a glance whether all VMs are closed.