mgmt: add face event notification and notification stream

refs: #1244

Change-Id: I14bd327be53bcb607b457d6cb4bd66bd28a2feaa
face: Implementing new "isOnDemand" flag

This flags replaces isPermanent flag in datagram faces, but with the
reversed logic (isPermanent = !isOnDemand)

Change-Id: I37ba604e5f105ca95a79a08b8cfc3d640df8b412
Refs: #1376