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/monitor-setup.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+if [ 1 -lt "$(xrandr -q | grep " connected" | wc -l)" ]; then
+	# scale second monitor to 3200x1800 and put to the left
+	xrandr --output eDP1 --auto --pos 3200x0 --primary --output DP1 --auto --scale-from 3200x1800 --pos 0x0 --fb 6400x1800
+	killall -q polybar
+	while pgrep -x polybar >/dev/null; do sleep 1; done
+else
+	xrandr --output eDP1 --auto --output DP1 --off
+fi
+
+"${XDG_CONFIG_HOME:-$HOME/.config}/polybar/launch.sh" &