nn_device now forwards protocol in addition to the message body

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
BUS protocol added

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Bus socket filters out  messages sent by itself

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Changed node ID in bus pattern from 32 bit integet to 64 bit one

Given that this is basically the 'birthday problem', with 32 bit
node IDs there's a non-negligible chance of collision. Given that
bus pattern only scales to local deployments (10s or 100s of nodes)
64 bit node ID should be reasonable safe.

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>