p910nd: Run as non-root by default

We add the necessary Makefile, hotplug, config, and init bits
so that p910nd daemon runs as user:group p910nd:lp by default.
This eliminates an unnecessary root daemon.

The hotplug script sets the permissions of the USB lp
device(s) to read-write owner and group and no access to
anyone else, and sets owner root, group lp.

This is allows sufficient privileges to p910nd
to do it's job.

(cherry-pick 932c76fa74)

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

net/p910nd/files/p910nd.hotplug

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+case "$ACTION" in
+        add)
+		[ -n "${DEVNAME}" ] && [ "${DEVNAME##usb/lp*}" = "" ] && {
+			chmod 660 /dev/"$DEVNAME"
+			chgrp lp /dev/"$DEVNAME"
+		}
+                ;;
+        remove)
+                # device is gone
+                ;;
+esac