Fixed reference to freed object.
Remove links to/from peers when they log-out.
Allow monitors to receive device /sync messages even if they share an admin.
Fixed bug when removing monitors that share admins with a device: some OSC handlers are required by both monitors and devices.
Add active ping to links; remove expired links if e.g. a device crashes. Any automatic restoration of links and connection on restart should be handled by a session-manager such as MASH.