app-window: Present window when machine activated
app-window: Present window when machine activated

This presents a machine's window if the machine is activated and is
already running in a window, otherwise it creates a new window for the
machine.

This is needed to make multiple windows possible.

https://bugzilla.gnome.org/show_bug.cgi?id=734486

vbenes/gnome-boxes,vbenes/gnome-boxes