A Tunnel Zone Mapper

This observable class can be used by the agent to retrieve a tunnel zone
simulation object, which contains the IP addresses of the hosts in this
tunnel zone.

Ref: MN-3066

Change-Id: I0290a04dab7e116bd1b037bf44c9413551730b49
Signed-off-by: Nicolas Schiper <nicolas@midokura.com>
Merge "A Tunnel Zone Mapper"