add support for device changes events

[benoitc]

UPNP, PMP and PCP allows the user to receive broadcasted events when their address change. This would allow the application to eventually broadcast a new external address if needed.

TODO

support the following specs:

• * upnp : http://upnp.org/specs/arch/UPnP-arch-DeviceArchitecture-v1.1.pdf (1.2.4)
• * PMP: https://tools.ietf.org/html/rfc6886#section-9.6
• * PCP: https://tools.ietf.org/html/rfc6887#section-11.5