Add tunnels table, loaded by assign_wrapper. This tables lists what
tunnels need to be created on each node; will be returned as a new tmcd command. Add nodeipportnum table, which is a hacky way to allocate non overlapping port numbers on physical nodes (when multiple virtual nodes are mapped to them). Used in assign_wrapper as a post pass over the trafgens table and the tunnels table. Add target_vname to virt_trafgens table as an aid in post passing.