upmpdcli: Add UPnP icon. Use procd for start/stop. 

Add uci config support for multiple instances

Signed-off-by: Ted Hess <thess@kitschensync.net>
My only concern here is if we should work with logical interfaces instead of the names of the l3 network devices. IIRC one could use `network_get_device` to determine the l3 network device name from the name of the logical interface.