feat: Add UNVR support (#11)

* Move partition mounts to PARTLABEL instead of paths
* Add dual firmware building support, specify the build type using the BOARD env var when using make
* Update to Unifi 4.0.5 pre-release firmware
* Move ulcmd init to be our "user interface" setup script, will handle LEDs on the UNVR4 in the future
* Update README with updated instructions
* Add udev rules to support /dev/boot which is what Unifi uses for some stupid reason for their emmc. This is required for systemd to mount correctly after chroot.
* Fixup small bugs found along the way

overlay/filesystem/usr/lib/init/boot/ubnt-ulcmd.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+# ULCMD wrapper, used to start ulcmd on the UNVR Pro, or setup the status LED on the UNVR-4
+
+case "$(ubnteeprom -systeminfo -key shortname)" in
+    "UNVRPRO")
+        # Is ulcmd running already? if so, assume it was not done via systemd so let's
+        # kill and respawn as this is our systemd entry script for the service, and we
+        # need to have it foregrounded as we act as the "daemon" here.
+        if ! pidof -q ulcmd; then
+            killall ulcmd
+        fi
+        # Restart ulcmd
+        exec ulcmd
+        ;;
+    "UNVR4")
+        # TODO: LED setup (2=white, 1=blue) against /sys/class/leds/ulogo_ctrl
+        # Start our "daemon" loop so systemd stays happy
+        while true; do
+            sleep 3600
+        done
+        ;;
+    *)
+        exit 1
+        ;;
+esac