sane-backends: run (xinetd) saned as non-root

saned requires write access scanner USB bus for its process and
to usblp/bind in order to rebind multifunctional printers back
to usblp (for printing with p910nd).

A hotplug script monitor new USB devices for scanners. Scanners
are detected by searching /usr/share/sane/<vendor>-<backend>.usbid
for the device product_id.

The package saned creates user saned:scanners. Access is granted to
group scanners.

The default xinetd conf was updated to run as saned:scanner.

sane-daemon pkg now has a postinst trigger that runs udevtrigger for
granting perms where there are connected scanners during installation.

Existing hotplug scripts from hplip were removed. They were mostly
useless.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>

utils/hplip/files/20-hplip

@@ -1,20 +0,0 @@
-#!/bin/sh
-
-# Copyright (C) 2009 OpenWrt.org
-
-
-case "$ACTION" in
-        add)
-                # You have to figure out your PRODUCT id. Uncomment the line below,
-                # attach and detach your HP USB printer to find your id in /tmp/hplip.test.
-                # It will look like "Found 3f0/1717/100 on /proc/bus/usb/002/009"
-                # Replace 3f0/1717/100 below with your id.
-                #
-                # echo "Found $PRODUCT on $DEVICE" > /tmp/hplip.test
-
-                [ "$PRODUCT" = "3f0/1717/100" ] && chown nobody $DEVICE && chmod 666 $DEVICE
-                ;;
-        remove)
-                # device is gone
-                ;;
-esac