p910nd: Run as non-root by default

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 932c76fa740acb0d68a46b78e2bc0eafd5fe13d6)

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