[Feature]Add option to show main window

[Rainmaker]

When a VM is started via the commandline, i.e. VirtualBoxManage, there is no way to open the main window. Within GNOME3 (and possibly other window managers), when starting VirtualBox, it switches to the running VM.

The same is true when doing the following:

• Start VB
• Start a couple of VMs
• Close the main window

Now, there's no way to get back to the main window. The only way is to start a second instance (by using a terminal), but via the GNOME3 itself, it can't easily be recovered.

This is strictly not a VB issue. However, it should be pretty easy to add a option somewhere under File or even Help to show the main window.

[Frank Mehnert]

I don't see the point. The main window (we denote it as VM selector) can be started just from the GNOME menu or by executing 'VirtualBox'.