IPv4MulticastRoute: rename parent/child to in/out
AnsaRoutingTable: removed unneeded override
AnsaRoutingTable: use inherited 'multicastRoutes' field
make AnsaIPv4MulticastRoute compatible with IPv4MulticastRoute

AnsaIPv4MulticastRoute stored its in and out interfaces in private fields
that was not accessible by IPv4. Now it uses the inInterface/outInterfaces
fields inherited from IPv4MulticastRoute.