Multi monitor support

When restarting i3 check for connected second monitor: scale it and
restart polybar if there is one.
Put polybar tray on the main monitor.
Do not kill polybar and relaunch it when restarting i3, but restart it
using ipc (much faster).

.config/i3/config

@@ -170,7 +170,7 @@ bindsym $mod+r mode "resize"
 #        status_command i3blocks
 #        position top
 # }
-exec_always --no-startup-id ~/.config/polybar/launch.sh &
+exec_always --no-startup-id ~/.config/i3/monitor-setup.sh &
 
 # Touchpad configuration
 set $touchpad DLL082A:01 06CB:76AF Touchpad